[contents] _________________________________________________________________ W3C Techniques for User Agent Accessibility Guidelines 1.0 W3C Working Draft 8 March 2000 This version: http://www.w3.org/WAI/UA/WD-UAAG10-TECHS-20000308 (plain text, gzip PostScript, gzip PDF, gzip tar file of HTML, zip archive of HTML) Latest version: http://www.w3.org/WAI/UA/UAAG10-TECHS Previous version: http://www.w3.org/TR/2000/WD-UAAG10-TECHS-20000128 Editors: Jon Gunderson, University of Illinois at Urbana-Champaign Ian Jacobs, W3C Copyright ©1999 - 2000 W3C® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply. _________________________________________________________________ Abstract This document provides techniques for satisfying the checkpoints defined in "User Agent Accessibility Guidelines 1.0" [UAAG10]. These techniques cover the accessibility of user interfaces, content rendering, application programming interfaces (APIs), and languages such as the Hypertext Markup Language (HTML), Cascading Style Sheets (CSS) and the Synchronized Multimedia Integration Language (SMIL). This document is part of a series of accessibility documents published by the Web Accessibility Initiative (WAI) of the World Wide Web Consortium (W3C). Status of this document This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C. This is a W3C Working Draft for review by W3C Members and other interested parties. It is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress". This is work in progress and does not imply endorsement by, or the consensus of, either W3C or participants in the WAI User Agent (UA) Working Group. While User Agent Accessibility Guidelines 1.0 strives to be a stable document (as a W3C Recommendation), the current document is expected to evolve as technologies change and content developers discover more effective techniques for designing accessible Web sites and pages. Please send comments about this document, including suggestions for additional techniques, to the public mailing list w3c-wai-ua@w3.org (public archives). This document has been produced as part of the Web Accessibility Initiative. The goals of the User Agent Working Group are described in the charter. A list of the Working Group participants is available. A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR. Table of contents * Abstract * Status of this document * 1 Introduction + 1.1 How the techniques are organized + 1.2 Related resources + 1.3 Document conventions + 1.4 Priorities * 2 User agent accessibility guidelines + 1. Support input and output device-independence. + 2. Ensure user access to all content. + 3. Allow the user to turn off rendering or stop behavior that may reduce accessibility. + 4. Ensure user control of styles. + 5. Observe system conventions and standard interfaces. + 6. Implement accessible specifications. + 7. Provide navigation mechanisms. + 8. Orient the user. + 9. Notify the user of content and viewport changes. + 10. Allow configuration and customization. + 11. Provide accessible product documentation and help. * 3 Accessibility topics + 3.1 Access to content + 3.2 User control of style + 3.3 Link techniques + 3.4 List techniques + 3.5 Table techniques + 3.6 Image map techniques + 3.7 Frame techniques + 3.8 Form techniques + 3.9 Generated content techniques + 3.10 Script and applet techniques + 3.11 Input configuration techniques + 3.12 Synthesized speech techniques * 4 Appendix: Accessibility features of some operating systems * 5 Appendix: Loading assistive technologies for access to the document object model * 6 Appendix: Glossary * 7 Acknowledgments * 8 References * 9 Resources + 9.1 Operating system and programming guidelines + 9.2 User agents and other tools + 9.3 Accessibility resources + 9.4 Standards resources _________________________________________________________________ 1 Introduction This document provides some suggestions for satisfying the requirements of the "User Agent Accessibility Guidelines 1.0" [UAAG10]. The techniques listed in this document are not required for conformance to the Guidelines. These techniques are not necessarily the only way of satisfying the checkpoint, nor are they necessarily a definitive set of requirements for satisfying a checkpoint. 1.1 How the techniques are organized Section 2 of this document reproduces the guidelines and checkpoints of the User Agent Accessibility Guidelines 1.0 [UAAG10]. Each checkpoint definition includes a link to the checkpoint definition in [UAAG10]. Each checkpoint definition is followed by a list of techniques, information about related resources, and references to the accessibility topics in section 3. These accessibility topics may apply to more than one checkpoint and so have been split off into stand-alone sections. Note. Some of the techniques in this document are appropriate for assistive technologies. 1.2 Related resources "Techniques for User Agent Accessibility Guidelines 1.0" and the Guidelines [UAAG10] are part of a series of accessibility guidelines published by the Web Accessibility Initiative (WAI). The series also includes "Web Content Accessibility Guidelines 1.0" [WCAG10] (and techniques [WCAG10-TECHS]) and "Authoring Tool Accessibility Guidelines 1.0" [ATAG10] (and techniques [ATAG10-TECHS]). 1.3 Document conventions The following editorial conventions are used throughout this document: * HTML element names are in uppercase letters (e.g., H1, BLOCKQUOTE, TABLE, etc.) * HTML attribute names are quoted in lowercase letters (e.g., "alt", "title", "class", etc.) 1.4 Priorities Each checkpoint in this document is assigned a priority that indicates its importance for users with disabilities. [Priority 1] This checkpoint must be satisfied by user agents, otherwise one or more groups of users with disabilities will find it impossible to access the Web. Satisfying this checkpoint is a basic requirement for enabling some people to access the Web. [Priority 2] This checkpoint should be satisfied by user agents, otherwise one or more groups of users with disabilities will find it difficult to access the Web. Satisfying this checkpoint will remove significant barriers to Web access for some people. [Priority 3] This checkpoint may be satisfied by user agents to make it easier for one or more groups of users with disabilities to access information. Satisfying this checkpoint will improve access to the Web for some people. _________________________________________________________________ 2 User agent accessibility guidelines This section lists each checkpoint of User Agent Accessibility Guidelines 1.0 [UAAG10] along with some possible techniques for satisfying it. Each checkpoint also links to more general accessibility topics where appropriate. Guideline 1. Support input and output device-independence. Checkpoints for user interface accessibility: 1.1 Ensure that every functionality available through the user interface is also available through every input device API supported by the user agent. Excluded from this requirement are functionalities that are part of the input device API itself (e.g., text input for the keyboard API, pointer motion for the pointer API, etc.) [Priority 1] (Checkpoint 1.1) Note. The device-independence required by this checkpoint applies to functionalities described by the other checkpoints in this document (e.g., installation, documentation, user agent user interface configuration, etc.). This checkpoint does not require user agents to use all operating system input device APIs, only to make the software accessible through those they do use. Techniques: Ensure that the user can do the following with all supported input devices: + Select content and operate on it. For example, if the user can select text with the mouse and make that text the content of a new link by pushing a button, they must also be able to do so through the keyboard and other supported devices. Other operations include cut, copy, and paste. + Set the focus. Ensure that software may be installed, uninstalled, and updated in a device-independent manner. + Navigate content. + Navigate links (refer to link techniques). + Use the graphical user interface menus. + Fill out forms. + Access documentation. + Configure the software. + Install, uninstall, and update the user agent software. Ensure that people with disabilities are involved in the design and testing of the software. __________________________________________________________ 1.2 Use the standard input and output device APIs of the operating system. [Priority 1] (Checkpoint 1.2) Do not bypass the standard output APIs when rendering information (e.g., for reasons of speed, efficiency, etc.). For example, do not bypass standard APIs to manipulate the memory associated with rendered content, since assistive technologies monitor rendering through the APIs. Techniques: + Operating system and application frameworks provide standard mechanisms for communication with input devices. In the case of Windows, OS/2, the X Windows System, and Mac OS, the window manager provides Graphical User Interface (GUI) applications with this information through the messaging queue. In the case of non-GUI applications, the compiler run-time libraries provide standard mechanisms for receiving keyboard input in the case of desktop operating systems. Should you use an application framework such as the Microsoft Foundation Classes, the framework used must support the same standard input mechanisms. + Do not communicate directly with an input device; this may circumvent system messaging. For instance, in Windows, do not open the keyboard device driver directly. It is often the case that the windowing system needs to change the form and method for processing standard input mechanisms for proper application coexistence within the user interface framework. + Do not implement your own input device event queue mechanism; this may circumvent system messaging. Some assistive technologies use standard system facilities for simulating keyboard and mouse events. From the application's perspective, these events are no different than those generated by the user's actions. The Journal Playback Hooks (in both OS/2 and Windows) is one example of an application that feeds the standard event queues. + Operating system and application frameworks provide standard mechanisms for using standard output devices. In the case of common desktop operating systems such as Windows, OS/2, and Mac OS, standard API are provided for writing to the display and the multimedia subsystems. + Do not render text in the form of a bitmap before transferring to the screen, since some screen readers rely on the user agent's offscreen model. Common operating system 2D graphics engines and drawing libraries provide functions for drawing text to the screen. Examples of this are the Graphics Device Interface (GDI) for Windows, Graphics Programming Interface (GPI) for OS/2, and for the X Windows System or Motif it is the X library (XLIB). + Do not communicate directly with an output device. + Do not draw directly to the video frame buffer. + Do not provide your own mechanism for generating pre-defined system sounds. + When writing textual information in a GUI operating system, use standard operating system APIs for drawing text. + Use operating system resources for rendering audio information. When doing so, do not take exclusive control of system audio resources. This could prevent an assistive technology such as a screen reader from speaking if they use software text-to-speech conversion. Also, in operating systems like Windows, a set of standard audio sound resources are provided to support standard sounds such as alerts. These preset sounds are used to activate SoundSentry graphical cue when a problem occurs; this benefits users with hearing disabilities. These queues may be manifested by flashing the desktop, active caption bar, or active window. It is important to use the standard mechanisms to generate audio feedback so that operating system or special assistive technologies can add additional functionality for the hearing disabled. + Enhance the functionality of standard system controls to improve accessibility where none is provided by responding to standard keyboard input mechanisms. For example provide keyboard navigation to menus and dialog box controls in the Apple Macintosh operating system. Another example is the Java Foundation Classes, where internal frames do not provide a keyboard mechanism to give them focus. In this case, you will need to add keyboard activation through the standard keyboard activation facility for Abstract Window Toolkit components. __________________________________________________________ 1.3 Ensure that the user can interact with all active elements in a device-independent manner. [Priority 1] (Checkpoint 1.3) For example, users who are blind or have physical disabilities must be able to activate text links, the links in a client-side image map, and form controls without a pointing device. Note. This checkpoint is an important special case of checkpoint 1.1. Techniques: + Refer to checkpoint 1.1 and checkpoint 1.5. + Refer to image map techniques. + In the "Document Object Model (DOM) Level 2 Specification" [DOM2], all elements may have associated behaviors. Assistive technologies should be able to activate these elements through the DOM. For example, a DOM 'focusin' event may cause a JavaScript function to construct a pull-down menu. Allowing programmatic activation of this function will allow users to operate the menu through speech input (which benefits users of voice browsers in addition to assistive technology users). Note that, for a given element, the same event may trigger more than one event handler, and assistive technologies must be able to activate each of them. Descriptive information about handlers can allow assistive technologies to select the most important functions for activation. This is possible in the Java Accessibility API [JAVAAPI], which provides an an AccessibleAction Java interface. This interface provides a list of actions and descriptions that enable selective activation. Refer also to checkpoint 5.3. __________________________________________________________ 1.4 Ensure that every functionality available through the user interface is also available through the standard keyboard API. [Priority 1] (Checkpoint 1.4) Note. This checkpoint is an important special case of checkpoint 1.1. The comment about low-level functionalities in checkpoint 1.1 applies to this checkpoint as well. Refer also to checkpoint 10.8. Techniques: + Apply the techniques for checkpoint 1.1 to the keyboard. + Account for author-supplied keyboard shortcuts, such as those specified by "accesskey" attribute in HTML 4.01 ([HTML4], section 17.11.2). + Allow the user to trigger event handlers (e.g., mouseover, mouseout, click, etc.) from the keyboard. + Test that all user interface components may be operable by software or devices that emulate a keyboard. Use SerialKeys and/or voice recognition software to test keyboard event emulation. __________________________________________________________ 1.5 Ensure every non-text message (e.g., prompt, alert, etc.) available through the user interface also has a text equivalent in the user interface. [Priority 1] (Checkpoint 1.5) Note. For example, if the user interface provides access to a functionality through a graphical button, ensure that a text equivalent for that button provides access to the same functionality from the user interface. If a sound is used to notify the user of an event, announce the event in text on the status bar as well. Refer also to checkpoint 5.7. Techniques: + Display text messages on the status bar of the user interface. + For graphical user interface elements such as proportional scroll bars, provide a text equivalent (e.g., a percentage of the document viewed). + Provide a text equivalent for beeps or flashes that are used to convey information. + Provide a text equivalent for audio user agent tutorials. Tutorials that use speech to guide a user through the operation of the user agent should also be available at the same time as graphical representations. + All user interface components that convey important information using sound should also provide alternate, parallel visual representation of the information for individuals who are deaf, hard of hearing, or operating the user agent in a noisy or silent environment where the use of sound is not practical. __________________________________________________________ Guideline 2. Ensure user access to all content. Checkpoints for content accessibility: 2.1 Ensure that the user has access to all content, including equivalent alternatives for content. [Priority 1] (Checkpoint 2.1) Refer to 5 for information about programmatic access to content. Techniques: + Some users benefit from concurrent access to primary and alternative content. For instance, users with low vision may want to view images (even imperfectly) but require a text equivalent for the image; the text may be rendered with a large font or as speech. + When content changes dynamically (e.g., due to scripts or content refresh), users must have access to the content before and after the change. + Refer to the section on access to content. + Refer to the section on link techniques. + Refer to the section on table techniques. + Refer to the section on frame techniques. + Refer to the section on form techniques. + Sections 10.4 ("Client Error 4xx") and 10.5 )"Server Error 5xx") of the HTTP 1.1 specification state that user agents should have the following behavior in case of these error conditions: Except when responding to a HEAD request, the server SHOULD include an entity containing an explanation of the error situation, and whether it is a temporary or permanent condition. These status codes are applicable to any request method. User agents SHOULD display any included entity to the user. + Make available information about abbreviation and acronym expansions. For instance, in HTML, look for abbreviations specified by the ABBR and ACRONYM elements. The expansion may be given with the "title" attribute. To provide expansion information, user agents may: o Allow the user to configure that the expansions be used in place of the abbreviations, o Provide a list of all abbreviations in the document, with their expansions (a generated glossary of sorts) o Generate a link from an abbreviation to its expansion. o Allow the user to query the expansion of a selected or input abbreviation. o If an acronym has no explicit expansion, user agents may look up in a glossary of acronyms for that page for another occurrence. Less reliably, the user agent may look for possible expansions (e.g., in parentheses) in surrounding context. __________________________________________________________ 2.2 For presentations that require user input within a specified time interval, allow the user to configure the time interval (e.g., to extend it or to cause the user agent to pause the presentation automatically and await user input before proceeding). [Priority 1] (Checkpoint 2.2) Techniques: + Render time-dependent links as a static list that occupies the same screen real estate; authors may create such documents in SMIL 1.0 [SMIL]. Include (temporal) context in the list of links. For example, provide the time at which the link appeared along with a way to easily jump to that portion of the presentation. + Provide easy-to-use controls (including both mouse and keyboard commands) to allow users to pause a presentation and advance and rewind by small or large time increments. Note. When a user must respond to a link by pausing the program and activating the link, the time dependent nature of the link does not change since the user must respond somehow in the predetermined time. The pause feature is only effective in conjunction with the ability to rewind to the link, or when the pause can be configured to stop the presentation automatically and require the user to respond before continuing, either by responding to the user input or by continuing with the flow of the document. + Highlight the fact that there are active elements in a presentation and allow users to navigate to and activate them. For example, indicate the presence of active elements on the status bar and allow the user to navigate among them with the keyboard or mouse. __________________________________________________________ 2.3 When the author has not supplied a text equivalent for content as required by the markup language, make available other author-supplied information about the content (e.g., object type, file name, etc.). [Priority 2] (Checkpoint 2.3) Techniques: Refer to techniques for missing equivalent alternatives of content. __________________________________________________________ 2.4 When a text equivalent for content is explicitly empty (i.e., an empty string), render nothing. [Priority 3] (Checkpoint 2.4) Techniques: + User agents should render nothing in this case because the author may specify a null text equivalent for content that has no function in the page other than as decoration. In this case, the user agent should not render generic labels such as "[INLINE]" or "[GRAPHIC]". + Allow the user to toggle the rendering of null text equivalents: between nothing and an indicator of a null equivalent (e.g., an icon with the text equivalent "EMPTY TEXT EQUIVALENT"). __________________________________________________________ Checkpoints for user interface accessibility: 2.5 If more than one equivalent alternative is available for content, allow the user to choose from among the alternatives. This includes the choice of viewing no alternatives. [Priority 1] (Checkpoint 2.5) For example, if a multimedia presentation has several captions (or subtitles) available, allow the user to choose from among them. Captions might differ in level of detail, address different reading levels, differ in natural language, etc. Techniques: + Refer to the section on access to content. + Allow users to choose more than one equivalent at a given time. For instance, multilingual audiences may wish to have captions in different natural languages on the screen at the same time. Users may wish to use both captions and auditory descriptions concurrently as well. + Make apparent through the user agent user interface which auditory tracks are meant to be played mutually exclusively. + In the user interface, construct a list of all available tracks from short descriptions provided by the author (e.g., through the "title" attribute). + Allow the user to configure different natural language preferences for different types of equivalents (e.g., captions and auditory descriptions). Users with disabilities may need to choose the language they are most familiar with in order to understand a presentation for which equivalent tracks are not all available in all desired languages. In addition, some users may prefer to hear the program audio in its original language while reading captions in another, fulfilling the function of subtitles or to improve foreign language comprehension. In classrooms, teachers may wish to configure the language of various multimedia elements to achieve specific educational goals. + Consider system level natural language preferences as the user's default language preference. However, do not send HTTP Accept-Language request headers ([RFC2616], section 14.4) based on the operating system preferences. First, there may be a privacy problem as indicated in RFC 2616, section 15.1.4 "Privacy Issues Connected to Accept Headers". Also, the operating system defines one language, while the Accept-Language request header may include many languages in different priorities. Automatic setting of accept-language the operating system language may result in the user receiving messages from servers that do not have a match to this single language although they have acceptable other languages to the users. The following image shows how users select a natural language preference in the Real Player. This setting, in conjunction with language markup in the presentation, determine what content is rendered. How user selects preferred natural language for captions in Real Player __________________________________________________________ 2.6 Allow the user to specify that text transcripts, collated text transcripts, captions, and auditory descriptions be rendered at the same time as the associated auditory and visual tracks. Respect author-supplied synchronization cues during rendering. [Priority 1] (Checkpoint 2.6) Techniques: + Captions and auditory descriptions may not make sense unless rendered synchronously with the primary content. For instance, if someone with hearing loss is watching a video presentation and reading associated captions, the captions must be synchronized with the audio so that the individual can use any residual hearing. For auditory descriptions, it is crucial that the primary auditory track and the auditory description track be synchronized to avoid having them both play at once, which would reduce the clarity of the presentation. + User agents that implement SMIL 1.0 ([SMIL]) should implement the "Accessibility Features of SMIL" [SMIL-ACCESS]. In particular, SMIL user agents should allow users to configure whether they want to view captions, and this user interface switch should be bound to the 'system-captions' test attribute. Users should be able to indicate a preference for receiving available auditory descriptions, but SMIL 1.0 does not include a mechanism equivalent to 'system-captions' for auditory descriptions. The next version of SMIL is expected to include a test attribute for auditory descriptions. Another SMIL 1.0 test attribute, 'system-overdub-or-captions', allows users to select between subtitles and overdubs in multilingual presentations. User agents should not interpret a value of 'caption' for this test attribute as meaning that the user prefers accessibility captions; that is the purpose of the 'system-captions' test attribute. When subtitles and accessibility captions are both available, deaf users may prefer to view captions, as they generally contain information not in subtitles: information on music, sound effects, who is speaking, etc. + User agents that play QuickTime movies should allow the user to turn on and off the different tracks embedded in the movie. Authors may use these alternate tracks to provide equivalent alternatives. The Apple QuickTime player currently provides this feature through the menu item "Enable Tracks." + User agents that play Microsoft Windows Media Object presentations should provide support for Synchronized Accessible Media Interchange (SAMI, a protocol for creating and displaying captions) and should allow users to configure how captions are viewed. In addition, user agents which play Microsoft Windows Media Object presentations should enable people to turn on and off other equivalent alternatives, including auditory description and alternate visual tracks. + For other formats, at a minimum, users must be able to turn on and off auditory descriptions and captions. __________________________________________________________ 2.7 For author-identified but unsupported natural languages, allow the user to request notification of language changes in content. [Priority 3] (Checkpoint 2.7) Techniques: + A user agent should treat the natural language of content as part of context information. When the language changes, the user agent should either render the content in the supported natural language or notify the user of the language change (if configured for notification). Rendering could involve speaking in the designated natural language in the case of an audio browser or screen reader. If the natural language is not supported, the language change notification could be spoken in the default language by a screen reader or audio browser. + Switching natural languages for blocks of content may be more helpful than switching for short phrases. In some language combinations (e.g., Japanese being the primary and English being the secondary or quoted language), short foreign language phrases are often well-integrated in the primary language. Dynamic switching for these short phrases may make the content sound unnatural and possibly harder to understand. + Refer to techniques for generated content, which may be used to insert text to indicate a language change. + Refer to techniques for synthesized speech. + Refer to checkpoint 2.7 and checkpoint 5.5. + For information on language codes, refer to [ISO639]. + If users do not want to see or hear blocks of content in another natural language, allow the user to suggest hiding that content (e.g., with style sheets). + Refer to "Character Model for the World Wide Web" [CHARMOD]. It contains basic definitions and models, specifications to be used by other specifications or directly by implementations, and explanatory material. In particular, this document addresses early uniform normalization, string identity matching, string indexing, and conventions for URIs. + Implement content negotiation so that users may specify language preferences. Or allow the user to choose a resource when several are available in different languages. + Use an appropriate glyph set when rendering visually and an appropriate voice set when rendering as speech. + Render characters with the appropriate directionality. Refer to the "dir" attribute and the BDO element in HTML 4.01 ([HTML4], sections 8.2 and 8.2.4 respectively). Refer also to the Unicode standard [UNICODE]. + A user agent may not be able to render all characters in a document meaningfully, for instance, because the user agent lacks a suitable font, a character has a value that may not be expressed in the user agent's internal character encoding, etc. In this case, section 5.4 of HTML 4.01 [HTML4] recommends the following for undisplayable characters: 1. Adopt a clearly visible (or audible), but unobtrusive mechanism to alert the user of missing resources. 2. If missing characters are presented using their numeric representation, use the hexadecimal (not decimal) form since this is the form used in character set standards. __________________________________________________________ Guideline 3. Allow the user to turn off rendering or stop behavior that may reduce accessibility. In addition to the techniques below, refer also to the section on user control of style. Checkpoints for content accessibility: 3.1 Allow the user to turn on and off rendering of background images. [Priority 1] (Checkpoint 3.1) Techniques: + Allow the user to turn off embedded or background images through the user agent user interface. Note that any equivalent alternatives for those images must still be available. + In CSS, background images may be turned on/off with the 'background' and 'background-image' properties ([CSS2], section 14.2.1). __________________________________________________________ 3.2 Allow the user to turn on and off rendering of background audio. [Priority 1] (Checkpoint 3.2) Techniques: + Allow the user to turn off background audio through the user agent user interface. + Authors sometimes specify background sounds with the "bgsound" attribute. Note. This attribute is not part of HTML 4.01 [HTML4]. + In CSS 2, background sounds may be turned on/off with the 'play-during' property ([CSS2], section 19.6). __________________________________________________________ 3.3 Allow the user to turn on and off rendering of video. [Priority 1] (Checkpoint 3.3) Techniques: + Allow the user to turn off video through the user agent user interface. Render a still image in its place. + Support the 'display' property in CSS ([CSS2], section 9.2.5). + Allow the user to hide a video presentation from view, even though it continues to play in the background. __________________________________________________________ 3.4 Allow the user to turn on and off rendering of audio. [Priority 1] (Checkpoint 3.4) Techniques: + Allow the user to turn off audio through the user agent user interface. + Support the 'display', 'play-during', and 'speak' properties in CSS 2 ([CSS2], sections 9.2.5, 19.6, and 19.5, respectively). __________________________________________________________ 3.5 Allow the user to turn on and off animated or blinking text. [Priority 1] (Checkpoint 3.5) Techniques: + Allow the user to turn off animated or blinking text through the user agent user interface (e.g., by pressing the Escape key to stop animations). Render static text in place of blinking text. + The BLINK element. Note. The BLINK element is not defined by a W3C specification. + The MARQUEE element. Note. The MARQUEE element is not defined by a W3C specification. + The 'blink' value of the 'text-decoration' property in CSS ([CSS2], section 16.3.1). __________________________________________________________ 3.6 Allow the user to turn on and off animations and blinking images. [Priority 1] (Checkpoint 3.6) Techniques: + Allow the user to turn off animated or blinking text through the user agent user interface (e.g., by pressing the Escape key to stop animations). Render a still image in its place. __________________________________________________________ 3.7 Allow the user to turn on and off support for scripts and applets. [Priority 1] (Checkpoint 3.7) Note. This is particularly important for scripts that cause the screen to flicker, since people with photosensitive epilepsy can have seizures triggered by flickering or flashing, particularly in the 4 to 59 flashes per second (Hertz) range. Techniques: + Peak sensitivity to flickering or flashing occurs at 20 Hertz. + Refer to the section on script techniques __________________________________________________________ 3.8 For automatic content changes specified by the author (e.g., redirection and content refresh), allow the user to slow the rate of change. [Priority 2] (Checkpoint 3.8) Techniques: + Alert the users to pages that refresh automatically and allow them to specify a refresh rate. + Allow the user to slow content refresh to once per 10 minutes. + Allow the user to stop automatic refresh, but indicate that content needs refreshing and allow the user to refresh the content by activating a button or link. Or, prompt the user and ask whether to continue with forwards. + Refer to the HTTP 1.1 specification [RFC2616] for information about redirection mechanisms. + Some HTML authors create a refresh effect by using a META element with http-equiv="refresh" and the refresh rate specified in seconds by the "content" attribute. __________________________________________________________ 3.9 Allow the user to turn on and off rendering of images. [Priority 3] (Checkpoint 3.9) Techniques: + Provide a simple command that allows users to turn on/off the rendering of images on a page. When images are turned off, render any associated equivalents. + Refer to techniques for checkpoint 3.1. __________________________________________________________ Guideline 4. Ensure user control of styles. In addition to the techniques below, refer also to the section on user control of style. Checkpoints for fonts and colors: 4.1 Allow the user to configure the size of text. [Priority 1] (Checkpoint 4.1) For example, allow the user to specify a font family and style directly through the user agent user interface or in a user style sheet. Or, allow the user to zoom or magnify content. Techniques: + Inherit text size information from user preferences specified for the operating system. + Use operating system magnification features. + Support the 'font-size' property in CSS ([CSS2], section 15.2.4). + Allow the user to override author-specified font sizes. + When scaling text, maintain size relationships among text of different sizes. __________________________________________________________ 4.2 Allow the user to configure font family. [Priority 1] (Checkpoint 4.2) Techniques: + Inherit font family information from user preferences specified for the operating system. + Support the 'font-family' property in CSS ([CSS2], section 15.2.2). + Allow the user to override author-specified font families. __________________________________________________________ 4.3 Allow the user to configure foreground color. [Priority 1] (Checkpoint 4.3) Techniques: + Inherit foreground color information from user preferences specified for the operating system. + Support the 'color' and 'border-color' properties in CSS 2 ([CSS2], sections 14.1 and 8.5.2, respectively). + Allow the user to specify minimal contrast between foreground and background colors, adjusting colors dynamically to meet those requirements. + Allow the user to override author-specified foreground colors. __________________________________________________________ 4.4 Allow the user to configure background color. [Priority 1] (Checkpoint 4.4) Techniques: + Inherit background color information from user preferences specified for the operating system. + Support the 'background-color' property (and other background properties) in CSS 2 ([CSS2], section 14.2.1). + Allow the user to override author-specified background colors. __________________________________________________________ Checkpoints for multimedia and audio presentations: 4.5 Allow the user to slow the presentation rate of audio, video, and animations. [Priority 1] (Checkpoint 4.5) Techniques: + Allowing the user to slow the presentation of video, animations, and audio will benefit individuals with specific learning disabilities, cognitive deficits, or those with normal cognition but newly acquired sensory limitations (such as the person who is newly blind, learning to use a screen reader). The same difficulty is common among individuals who have beginning familiarity with a natural language. + When changing the rate of audio, avoid pitch distortion. + Some formats do not allow changes in playback rate. __________________________________________________________ 4.6 Allow the user to start, stop, pause, advance, and rewind audio, video, and animations. [Priority 1] (Checkpoint 4.6) Techniques: + Allow the user to advance or rewind the presentation in increments. This is particularly valuable to users with physical disabilities who may not have fine control over advance and rewind functionalities. Allow users to configure the size of the increments. + If buttons are used to control advance and rewind, make the advance/rewind distances proportional to the time the user activates the button. After a certain delay, accelerate the advance/rewind. + There are well-known techniques for changing audio speed without introducing distortion. + Home Page Reader [HPR] lets users insert bookmarks in presentations. __________________________________________________________ 4.7 Allow the user to configure the position of text transcripts, collated text transcripts, and captions on graphical displays. [Priority 1] (Checkpoint 4.7) Techniques: + Support the CSS 2 'position' property ([CSS2], section 9.3.1). + Allow the user to choose whether captions appear at the bottom or top of the video area or in other positions. Currently authors may place captions overlying the video or in a separate box. Captions may block the user's view of other information in the video or on other parts of the screen, making it necessary to move the captions in order to view all content at once. In addition, some users may find captions easier to read if they can place them in a location best suited to their reading style. + Allow users to configure a general preference for caption position and to be able to fine tune specific cases. For example, the user may want the captions to be in front of and below the rest of the presentation. + Allow the user to drag and drop the captions to a place on the screen like any other viewport. To ensure device-independence, allow the user to enter the screen coordinates of one corner of the caption viewport. + It may be easiest to allow the user to position all parts of a presentation rather than trying to identify captions specifically. + Do not require users to edit the source code of the presentation to achieve the desired effect. __________________________________________________________ 4.8 Allow the user to configure the audio volume. [Priority 2] (Checkpoint 4.8) Techniques: + Support the CSS 2 'volume' property ([CSS2], section 19.2). + Allow the user to configure a volume level at the operating system level. __________________________________________________________ Checkpoints for synthesized speech: Refer also to techniques for synthesized speech. 4.9 Allow the user to configure synthesized speech playback rate. [Priority 1] (Checkpoint 4.9) Techniques: + Support the CSS 2 'speech-rate' property ([CSS2], section 19.8). __________________________________________________________ 4.10 Allow the user to configure synthesized speech volume. [Priority 1] (Checkpoint 4.10) Techniques: + Support the CSS 2 'volume' property ([CSS2], section 19.2). __________________________________________________________ 4.11 Allow the user to configure synthesized speech pitch, gender, and other articulation characteristics. [Priority 2] (Checkpoint 4.11) Techniques: + Implement the voice characteristic properties and speech properties of CSS 2: 'voice-family', 'pitch', 'pitch-range', 'stress', 'richness', 'speak-punctuation', and 'speak-numeral' ([CSS2], sections 19.8 and 19.9). __________________________________________________________ Checkpoints for user interface accessibility: 4.12 Allow the user to select from available author and user style sheets or to ignore them. [Priority 1] (Checkpoint 4.12) Note. By definition the browser's default style sheet is always present, but may be overridden by author or user styles. Techniques: + For HTML [HTML4], make available "class" and "id" information so that users can override styles. + Implement user style sheets. + Implement the "!important" semantics of CSS 2 ([CSS2], section 6.4.2). __________________________________________________________ 4.13 Allow the user to configure how the selection is highlighted (e.g., foreground and background color). [Priority 1] (Checkpoint 4.13) Techniques: + Netscape Navigator [NAVIGATOR] for X Windows uses resources to control the selection colors (*selectForeground and *selectBackground). + Support the CSS 2 "HighLightText and "Highlight" predefined color values ([CSS2], section 18.2). + Inherit selection information from user's settings for the operating system. __________________________________________________________ 4.14 Allow the user to configure how the content focus is highlighted (e.g., foreground and background color). [Priority 1] (Checkpoint 4.14) Techniques: + Support the CSS 2 ':focus' pseudo-class and dynamic outlines and focus of CSS 2 ([CSS2], sections 5.11.3 and 18.4.1, respectively). For example, the following rule will cause links with focus to appear with a blue background and yellow text. A:focus { background: blue; color: yellow } The following rule will cause TEXTAREA elements with focus to appear with a particular focus outline: TEXTAREA:focus { outline: thick black solid } + Inherit focus information from user's settings for the operating system. + Test the user agent to ensure that individuals who have low vision and use screen magnification software are able to follow highlighted item(s). __________________________________________________________ 4.15 Allow the user to configure how the focus changes. [Priority 2] (Checkpoint 4.15) For instance, allow the user to require that user interface focus not move automatically to a newly opened viewport. Techniques: + Allow the user to configure how current focus changes when a new viewport opens. For instance, the user might choose between these two options: 1. Do not change the focus when a window opens, but notify the user (e.g., with a beep, flash, and text message on the status bar). Allow the user to navigate directly to the new window when they choose to. 2. Change the focus when a window opens and use a subtle alert (e.g., a beep, flash, and text message on the status bar) to indicate that the focus has changed. + If a new viewport or prompt appears but focus does not move to it, notify assistive so that they may (discreetly) inform the user, allow querying, etc. __________________________________________________________ 4.16 Allow the user to configure viewports, prompts, and windows opened on user agent initiation. [Priority 2] (Checkpoint 4.16) For instance, allow the user to turn off viewport creation. Refer also to checkpoint 5.7. Techniques: + For HTML [HTML4], allow the user to control the process of opening a document in a new "target" frame or a viewport created by author-supplied scripts. For example, for target="_blank", open the window according to the user's preference. + For SMIL [SMIL], allow the user to control viewports created with the "new" value of the "show" attribute. + Allow users to turn off support for user agent initiated viewports entirely. + Prompt users before opening a viewport. For instance, for user agents that support CSS 2 [CSS2], the following rule will generate a message to the user at the beginning of link text for links that are meant to open new windows when followed: A[target=_blank]:before{content:"Open new window"} + Allow users to configure the size or position of the viewport and to be able to close the viewport (e.g., with the "back" functionality). __________________________________________________________ Guideline 5. Observe system conventions and standard interfaces. Checkpoints for content accessibility: 5.1 Provide programmatic read access to HTML and XML content by conforming to the W3C Document Object Model (DOM) Level 2 Core and HTML modules and exporting the interfaces they define. [Priority 1] (Checkpoint 5.1) Note. These modules are defined in DOM Level 2 [DOM2], chapters 1 and 2. Please refer to that specification for information about which versions of HTML and XML are supported and for the definition of a "read-only DOM. For content other than HTML and XML, refer to checkpoint 5.3. This checkpoint is an important special case of checkpoint 2.1. Techniques: + Information of particular importance to accessibility that must be available through the document object model includes: o Content, including equivalent alternatives. o The document structure (for navigation, creation of alternative views). o Style sheet information (for user control of styles). o Script and event handlers (for device-independent control of behavior). + Assistive technologies also require information about browser selection and focus mechanisms, which may not be available through the W3C DOM. + The W3C DOM is designed to be used on a server as well as a client, and so does not address some user interface-specific information (e.g., screen coordinates). + Refer to the appendix on loading assistive technologies for DOM access. + For information about rapid access to Internet Explorer's [IE] DOM through COM, refer to [BHO]. + Refer to the Java Weblets implementation of the DOM [JAVAWEBLET]. __________________________________________________________ 5.2 If the user can modify HTML and XML content through the user interface, provide the same functionality programmatically by conforming to the W3C Document Object Model (DOM) Level 2 Core and HTML modules and exporting the interfaces they define. [Priority 1] (Checkpoint 5.2) For example, if the user interface allows users to complete HTML forms, this must also be possible through the DOM APIs. Note. These modules are defined in DOM Level 2 [DOM2], chapters 1 and 2. Please refer to DOM Level 2 [DOM2] for information about which versions of HTML and XML are supported. For content other than HTML and XML, refer to checkpoint 5.3. This checkpoint is an important special case of checkpoint 2.1. Techniques: + Refer to techniques for checkpoint 5.1. __________________________________________________________ 5.3 For markup languages other than HTML and XML, provide programmatic access to content using standard APIs (e.g., platform-independent APIs and standard APIs for the operating system). [Priority 1] (Checkpoint 5.3) Note. This checkpoint addresses content not covered by checkpoints checkpoint 5.1 and checkpoint 5.2. This checkpoint is an important special case of checkpoint 2.1. Techniques: + Refer to techniques for checkpoint 5.5. __________________________________________________________ 5.4 Provide programmatic access to Cascading Style Sheets (CSS) by conforming to the W3C Document Object Model (DOM) Level 2 CSS module and exporting the interfaces it defines. [Priority 3] (Checkpoint 5.4) Note. This module is defined in DOM Level 2 [DOM2], chapter 5. Please refer to that specification for information about which versions of CSS are supported. This checkpoint is an important special case of checkpoint 2.1. Techniques: + Refer to techniques for checkpoint 5.1. __________________________________________________________ Checkpoints for user interface accessibility: 5.5 Provide programmatic read and write access to user agent user interface controls using standard APIs (e.g., platform-independent APIs such as the W3C DOM, standard APIs for the operating system, and conventions for programming languages, plug-ins, virtual machine environments, etc.) [Priority 1] (Checkpoint 5.5) For example, ensure that assistive technologies have access to information about the user agent's current input configuration so that they can trigger functionalities through keyboard events, mouse events, etc. Techniques: + Some operating system and programming language APIs support accessibility by providing a bridge between the standard user interface supported by the operating system and alternative user interfaces developed by assistive technologies. User agents that implement these APIs are generally more compatible with assistive technologies and provide accessibility at no extra cost. Some public APIs that promote accessibility include: o Microsoft Active Accessibility ([MSAA]) in Windows 95/98/NT versions. o Sun Microsystems Java Accessibility API ([JAVAAPI]) in Java Code. If the user agent supports Java applets and provides a Java Virtual Machine to run them, the user agent should support the proper loading and operation of a Java native assistive technology. This assistive technology can provide access to the applet as defined by Java accessibility standards. + Use standard user interface controls. Third-party assistive technology developers are more likely able to access standard controls than custom controls. If you must use custom controls, review them for accessibility and compatibility with third-party assistive technology. Ensure that they provide accessibility information through an API as is done for the standard controls. + Makes use of operating system level features. See the appendix of accessibility features for some common operating systems. + Inherit operating system settings related to accessibility (e.g., for fonts, colors, natural language preferences, input configurations, etc.). + Write output to and take input from standard system APIs rather than directly from hardware controls. This will enable the I/O to be redirected from or to assistive technology devices - for example, screen readers and Braille displays often redirect output (or copy it) to a serial port, while many devices provide character input, or mimic mouse functionality. The use of generic APIs makes this feasible in a way that allows for interoperability of the assistive technology with a range of applications. + For information about rapid access to Internet Explorer's [IE] DOM through COM, refer to [BHO]. __________________________________________________________ 5.6 Implement selection, content focus, and user interface focus mechanisms. [Priority 1] (Checkpoint 5.6) Refer also to checkpoint 7.1 and checkpoint 5.5. Note. This checkpoint is an important special case of checkpoint 5.5. Techniques: + Refer to Selection and Partial Selection of DOM Level 2 ([DOM2], section 8.2.2). + For information about focus in the Motif environment (under X Windows), refer to the OSF/Motif Style Guide [MOTIF]. __________________________________________________________ 5.7 Provide programmatic notification of changes to content and user interface controls (including selection, content focus, and user interface focus). [Priority 1] (Checkpoint 5.7) Techniques: + Refer to "mutation events" in DOM Level 2 [DOM2]. This module of DOM 2 allows assistive technologies to be informed of changes to the document tree. + Allow assistive technologies to register for some, but not all, events. + Refer also to information about monitoring HTML events through the document object model Internet Explorer [IE]. __________________________________________________________ Refer also to checkpoint 5.5. 5.8 Ensure that programmatic exchanges proceed in a timely manner. [Priority 2] (Checkpoint 5.8) For example, the programmatic exchange of information required by other checkpoints in this document must be efficient enough to prevent information loss, a risk when changes to content or user interface occur more quickly than the communication of those changes. The techniques for this checkpoint explain how developers can reduce communication delays, e.g., to ensure that assistive technologies have timely access to the document object model and other information needed for accessibility. Techniques: + Please refer to the appendix that explains how to load assistive technologies for DOM access. __________________________________________________________ 5.9 Follow operating system conventions and accessibility settings. In particular, follow conventions for user interface design, default keyboard configuration, product installation, and documentation. [Priority 2] (Checkpoint 5.9) Refer also to checkpoint 10.2. Techniques: + Refer to techniques for checkpoint 1.2. + Refer to techniques for checkpoint 5.5. + Refer to techniques for checkpoint 10.2. + Follow operating system and application environment (e.g., Java) conventions for loading assistive technologies. Refer to the appendix on loading assistive technologies for DOM access for information about how an assistive technology developer can load its software into a Java Virtual Machine. + Evaluate the standard interface controls on the target platform against any built-in operating system accessibility functions and be sure the user agent operates properly with all these functions. For example, be attentive to the following features: o Microsoft Windows supports an accessibility function called "High Contrast". Standard window classes and controls automatically support this setting. However, applications created with custom classes or controls must understand how to work with the "GetSysColor" API to ensure compatibility with High Contrast. o Apple Macintosh supports an accessibility function called "Sticky Keys". Sticky Keys operate with keys the operating system recognizes as modifier keys, and therefore a custom control should not attempt to define a new modifier key. + Follow accessibility guidelines for specific platforms: o "Macintosh Human Interface Guidelines" [APPLE-HI] o "IBM Guidelines for Writing Accessible Applications Using 100% Pure Java" [JAVA-ACCESS]. o "An ICE Rendezvous Mechanism for X Window System Clients" [ICE-RAP]. o "Information for Developers About Microsoft Active Accessibility" [MSAA]. o "The Inter-Client communication conventions manual" [ICCCM]. o "Lotus Notes accessibility guidelines" [NOTES-ACCESS]. o "Java accessibility guidelines and checklist" [JAVA-CHECKLIST]. o "The Java Tutorial. Trail: Creating a GUI with JFC/Swing" [JAVA-TUT]. o "The Microsoft Windows Guidelines for Accessible Software Design" [MS-SOFTWARE]. + Follow general guidelines for producing accessible software: o "Accessibility for applications designers" [MS-ENABLE]. o "Application Software Design Guidelines" [TRACE-REF]. o "Designing for Accessibility" [SUN-DESIGN]. o "EITAAC Desktop Software standards" [EITAAC]. o "Requirements for Accessible Software Design" [ED-DEPT]. o "Software Accessibility" [IBM-ACCESS]. o Towards Accessible Human-Computer Interaction" [SUN-HCI]. o "What is Accessible Software" [WHAT-IS]. o Accessibility guidelines for Unix and X Window applications [XGUIDELINES]. __________________________________________________________ Guideline 6. Implement accessible specifications. Checkpoints for content accessibility: 6.1 Implement the accessibility features of supported specifications (markup languages, style sheet languages, metadata languages, graphics formats, etc.). [Priority 1] (Checkpoint 6.1) Techniques: + Features that are known to promote accessibility should be made obvious to users and easy to find in the user interface and in documentation. + The accessibility features of Cascading Style Sheets ([CSS1], [CSS2]) are described in "Accessibility Features of CSS" [CSS-ACCESS]. Note that CSS 2 includes properties for configuring synthesized speech styles. + The accessibility features of SMIL 1.0 [SMIL] are described in "Accessibility Features of SMIL" [SMIL-ACCESS]. + The following is a list of accessibility features of HTML 4.01 [HTML4] in addition to those described in techniques for checkpoint 2.1: o The CAPTION element (section 11.2.2) for rich table captions. o Table elements THEAD, TBODY, and TFOOT (section 11.2.3), COLGROUP and COL (section 11.2.4) that group table rows and columns into meaningful sections. o Attributes "scope", "headers", and "axis" (section 11.2.6) that non-visual browsers may use to render a table in a linear fashion, based on the semantically significant labels. o The "tabindex" attribute (section 17.11.1) for assigning the order of keyboard navigation within a document. o The "accesskey" attribute (section 17.11.2) for assigning keyboard commands to active components such as links and form controls. __________________________________________________________ 6.2 Conform to W3C Recommendations when they are appropriate for a task. [Priority 2] (Checkpoint 6.2) For instance, for markup, implement HTML 4.01 [HTML4] or XML 1.0 [XML]. For style sheets, implement CSS ([CSS1], [CSS2]). For mathematics, implement MathML [MATHML]. For synchronized multimedia, implement SMIL 1.0 [SMIL]. For access to the structure of HTML or XML documents, implement the DOM [DOM2]. Refer also to guideline 5. Note. For reasons of backward compatibility, user agents should continue to support deprecated features of specifications. The current guidelines refer to some deprecated language features that do not necessarily promote accessibility but are widely deployed. Information about deprecated language features is generally part of the language's specification. Techniques: + The requirement of this checkpoint is to implement at least one W3C Recommendation that is available and appropriate for a particular task. For example, user agents would satisfy this checkpoint by implementing the Portable Network Graphics 1.0 specification [PNG] for raster images. In addition, user agents may implement other image formats such as JPEG, GIF, etc. + If more than one version or level of a W3C Recommendation is appropriate for a particular task, user agents are encouraged to implement the latest version. + Specifications that become W3C Recommendations after a user agent's development cycles permit input are not considered "available" in time for that version of the user agent. + Refer to the list of W3C technical reports. Each specification defines what conformance means for that specification. + W3C encourages the public to review and comment on specifications at all times during their development, from Working Draft to Candidate Recommendation (for implementation experience) to Proposed Recommendation. However, readers should remain aware that a W3C specification do not represent consensus in the Working Group, Web Community, and W3C Membership until it becomes a Recommendation. + Use the W3C validation services: o HTML and XML Validator service [VALIDATOR]. o CSS Validator service [CSSVALIDATOR]. __________________________________________________________ Guideline 7. Provide navigation mechanisms. Checkpoints for user interface accessibility: 7.1 Allow the user to navigate viewports (including frames). [Priority 1] (Checkpoint 7.1) Note. For example, when all frames of a frameset are displayed side-by-side, allow the user to navigate among them with the keyboard. Or, when frames are accessed or viewed one at a time (e.g., by a text browser or speech synthesizer), provide a list of links to other frames. Navigating into a viewport makes it the current viewport. Techniques: + Refer to the frame techniques. Some operating systems provide a means to navigate among all open windows using multiple input devices (e.g., keyboard and mouse). This technique would suffice for switching among user agent viewports that are separate windows. However, user agents may also provide a mechanism to shift the user interface focus among user agent windows, independent of the standard operating system mechanism. __________________________________________________________ 7.2 For user agents that offer a browsing history mechanism, when the user returns to a previous viewport, restore the point of regard in the viewport. [Priority 1] (Checkpoint 7.2) For example, when users navigate "back" and "forth" among viewports, they should find the viewport position where they last left it. Techniques: + If the user agent allows the user to browse multimedia or audio presentations, when the user leaves one presentation for another, pause the presentation. When the user returns to a previous presentation, allow the user to restart the presentation where it was paused (i.e., return the point of regard to the same place in space and time). Note. This may be done for a presentation that is available "completely" but not for a "live" stream or any part of a presentation that continues to run in the background. + When the user returns to a page after following a link, restore content focus to that link. + Refer to the HTTP 1.1 specification for information about history mechanisms ([RFC2616], section 13.13). __________________________________________________________ 7.3 Allow the user to navigate all active elements. [Priority 1] (Checkpoint 7.3) Navigation may include non-active elements in addition to active elements. Note. This checkpoint is an important special case of checkpoint 7.6. Techniques: Sequential navigation techniques + Allow the user to sequentially navigate all active elements using a single keystroke. Many user agents today allow users to navigate sequentially by repeating a key combination -- for example, using the Tab key for forward navigation and Shift-Tab for reverse navigation. Because the Tab key is typically on one side of the keyboard while arrow keys are located on the other, users should be allowed to configure the user agent so that sequential navigation is possible with keys that are physically closer to the arrow keys. Refer also to checkpoint 10.4. + Provide other sequential navigation mechanisms for particular element types or semantic units. For example "Find the next table" or "Find the previous form". For more information about sequential navigation of form controls and form submission, refer to techniques for [#info-form-submit]. + Maintain a logical element navigation order. For instance, users may use the keyboard to navigate among elements or element groups using the arrow keys within a group of elements. One example of a group of elements is a set of radio buttons. Users should be able to navigate to the group of buttons, then be able to select each button in the group. Similarly, allow users to navigate from table to table, but also among the cells within a given table (up, down, left, right, etc.) + The default sequential navigation order should respect the conventions of the natural language of the document. Thus, for most left-to-right languages, the usual navigation order is top-to-bottom and left-to-right. Thus, for right-to-left languages, the order would be top-to-bottom and right-to-left. + Respect author-supplied information about navigation order (e.g., the "tabindex" attribute in HTML 4 [HTML4], section 17.11.1). Allow users to override the author-supplied navigation order (e.g., by offering an alphabetized view of links or other orderings). + Give the users the option of navigating to and activating a link, or just moving the content focus to the link. First-time users of a page may want access to link text before deciding whether to follow the link (activate). More experienced users of a page might prefer to follow the link directly, without the intervening content focus step. + In Java, a component is part of the sequential navigation order when added to a panel and its isFocusTraversable() method returns true. A component can be removed from the navigation order by extending the component, overloading this method, and returning false. The following view from Jaws for Windows [JFW] allows users to navigate to links in a document and activate them independently. Users may also configure the user agent to navigate visited links, unvisited links, or both. Users may also change the sequential navigation order, sorting links alphabetically or leaving them in the logical tabbing order. Jaws for Windows Links List view Direct navigation techniques + Excessive use of sequential navigation can reduce the usability of software for both disabled and non-disabled users. + Some useful types of direct navigation include: navigation based on position (e.g., all links are numbered by the user agent), navigation based on element content (e.g., the first letter of text content), direct navigation to a table cell by its row/column position, and searching (e.g., based on form control text, associated labels, or form control names). + Document available direct navigation mechanisms. __________________________________________________________ 7.4 Allow the user to choose to navigate only active elements. [Priority 2] (Checkpoint 7.4) Techniques: + Apply the techniques of checkpoint 7.3 to active elements only. __________________________________________________________ 7.5 Allow the user to search for rendered text content, including rendered text equivalents. [Priority 2] (Checkpoint 7.5) Note. Use operating system conventions for marking the result of a search (e.g., selection or content focus). Techniques: + Allow users to search for (human-readable) element content and attribute values. + Allow users to search forward and backward from the point of regard, the beginning of document, or the end of the document. + Allow users to search the document source view. + For forms, allow users to find controls that must be changed by the user before submitting the form. Allow users to search on labels as well as content of some controls. + Allow the user to search among just text equivalents of other content. + For multimedia presentations: o Allow users to search and examine time-dependent media elements and links in a time-independent manner. For example, present a static list of time-dependent links. o Allow users to find all media elements active at a particular time in the presentation. o Allow users to view a list of all media elements or links of the presentations sorted by start or end time or alphabetically. o For frames, allow users to search for content in all frames, without having to be in a particular frame. o It may be confusing to allow users to search for text content that is not rendered (and thus that they have not viewed); it will be difficult to move the selection if text is found. If the user agent allows this type of search, notify the user of this particular search mode. __________________________________________________________ 7.6 Allow the user to navigate according to structure. [Priority 2] (Checkpoint 7.6) For example, allow the user to navigate familiar elements of a document: paragraphs, tables and table cells, headers, lists, etc. Note. Use operating system conventions to indicate navigation progress (e.g., selection or content focus). Techniques: + Use the DOM [DOM2] as the basis of structured navigation. However, for well-known markup languages such as HTML, structured navigation should take advantage of the structure of the source tree and what is rendered. + Allow navigation based on commonly understood document models, even if they do not adhere strictly to a Document Type Definition (DTD). navigation. For instance, in HTML, although headers (H1-H6) are not containers, they may be treated as such for the purpose of navigation. Note that they should be properly nested. + Allow the user to limit navigation to the cells of a table (notably left and right within a row and up and down within a column). Navigation techniques include keyboard navigation from cell to cell (e.g., using the arrow keys) and page up/down scrolling. Refer to the section on table navigation. + Allow depth-first as well as breadth-first navigation. + Provide context-sensitive navigation. For instance, when the user navigates to a list or table, provide locally useful navigation mechanisms (e.g., within a table, cell-by-cell navigation) using similar input commands. + From a given element, allow navigation to the next or previous sibling, up to the parent, and to the end of an element. + Allow users to navigate synchronized multimedia presentations in time. Refer also to checkpoint 4.6. + Allow the user to navigate characters, words, sentences, paragraphs, screenfuls, and other pieces of text content that depend on natural language. This benefits users of speech-based user agents and has been implemented by several screen readers, including Winvision [WINVISION], Window-Eyes [WINDOWEYES], and Jaws for Windows [JFW]. + Allow users to skip author-supplied navigation mechanisms such as navigation bars. For instance, navigation bars at the top of each page at a Web site may force users with screen readers or some physical disabilities to wade through many links before reaching the important information on the page. User agents may facilitate browsing for these users by allowing them to skip recognized navigation bars (e.g., through a configuration option). Some techniques for this include: 1. Providing a functionality to jump to the first non-link content. 2. In HTML, the MAP element may be used to mark up a navigation bar (even when there is no associated image). Thus, users might ask that MAP elements not be rendered in order to hide links inside the MAP element. Note. Starting in HTML 4.01, the MAP element allows block content, not just AREA elements. + The following is a summary of ideas provided by the National Information Standards Organization [NISO]: A talking book's "Navigation Control Center" (NCC) resembles a traditional table of contents, but it is more. It contains links to all headings at all levels in the book, links to all pages, and links to any items that the reader has chosen not to have read. For example, the reader may have turned off the automatic reading of footnotes. To allow the user to retrieve that information quickly, the reference to the footnote is placed in the NCC and the reader can go to the reference, understand the context for the footnote, and then read the footnote. Once the reader is at a desired location and wishes to begin reading, the navigation process changes. Of course, the reader may elect to read sequentially, but often some navigation is required (e.g., frequently people navigate forward or backward one word or character at a time). Moving from one sentence or paragraph at a time is also needed. This type of local navigation is different from the global navigation used to get to the location of what you want to read. It is frequently desirable to move from one block element to the next. For example, moving from a paragraph to the next block element which may be a list, blockquote, or sidebar is the normally expected mechanism for local navigation. __________________________________________________________ 7.7 Allow the user to configure structured navigation. [Priority 3] (Checkpoint 7.7) For example, allow the user to navigate only paragraphs, or only headers and paragraphs, etc. Techniques: + Allow the user to navigate by element type. + Allow the user to navigate HTML elements that share the same "class" attribute. + Allow the user to expand or shrink portions of the structured view (configure detail level) for faster access to important parts of content. __________________________________________________________ Guideline 8. Orient the user. Checkpoints for content accessibility: 8.1 Make available to the user the author-specified purpose of each table and the relationships among the table cells and headers. [Priority 1] (Checkpoint 8.1) For example, provide information about table headers, how headers relate to cells, table summary information, cell position information, table dimensions, etc. Refer also to checkpoint 5.3. Note. This checkpoint is an important special case of checkpoint 2.1. Techniques: + Refer to the section on table techniques + Allow the user to navigate to a table cell and query the cell for metadata (e.g., by activating a menu or keystroke). The following image shows how Internet Explorer [IE] provides cell header information through the context ("right-click") menu: Internet Explorer context menu item to display table cell header information __________________________________________________________ 8.2 Indicate to the user whether a link has been visited. [Priority 2] (Checkpoint 8.2) Note. This checkpoint is an important special case of checkpoint 8.4. Techniques: + Do not rely on color alone. Refer to the visited links example in the section on generated content techniques. + Refer to techniques for checkpoint 7.3. + Refer to the section on link techniques. __________________________________________________________ 8.3 Indicate to the user whether a link has been marked up to indicate that following it will involve a fee. [Priority 2] (Checkpoint 8.3) Note. This checkpoint is an important special case of checkpoint 8.4. The W3C specification "Common Markup for micropayment per-fee-links" [MICROPAYMENT] describes how authors may mark up micropayment information in an interoperable manner. Techniques: + Use standard, accessible interface controls to present information about fees and to prompt the user to confirm payment. + For a link that has content focus, allow the user to query the link for fee information (e.g., by activating a menu or keystroke). + Refer to the section on link techniques. __________________________________________________________ 8.4 To help the user decide whether to follow a link, make available link information supplied by the author and computed by the user agent. [Priority 3] (Checkpoint 8.4) Information supplied by the author includes link content, link title, whether the link is internal, whether it involves a fee, and hints on the content type, size, or natural language of the linked resource. Information computed by the user agent includes whether the user has already visited the link. Note. User agents are not required to retrieve the resource designated by a link as part of computing information about the link. Techniques: + For a link that has content focus, allow the user to query the link for information (e.g., by activating a menu or keystroke). + Refer to the section on link techniques. The following image shows how Opera [OPERA] allows the user to configure link rendering, including the identification of visited links. The Opera dialog box for configuring the rendering of links __________________________________________________________ Checkpoints for user interface accessibility: 8.5 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current viewport, selection, and content focus. [Priority 1] (Checkpoint 8.5) Note. This includes highlighting and identifying frames. Note. This checkpoint is an important special case of checkpoint 1.1. Refer also to checkpoint 8.4. Techniques: + If colors are used to highlight the current viewport, selection, or content focus, allow the user to configure these colors. + Provide a setting that causes a window that is the current viewport to pop to the foreground. + Provide a setting that causes a window that is the current viewport to be maximized automatically. For example, maximize the parent window of the browser when launched, and maximize each child window automatically when it receives focus. Maximizing does not necessarily mean occupying the whole screen or parent window; it means expanding the current window so that users have to scroll horizontally or vertically as little as possible. + If the current viewport is a frame or the user does not want windows to pop to the foreground, use colors, reverse videos, or other graphical clues to indicate the current viewport. + For speech or Braille output, use the frame or window title to identify the current viewport. Announce changes in the current viewport. + Use operating system conventions, for specifying selection and content focus (e.g., schemes in Windows). + Support the ':hover', ':active', and ':focus' pseudo-classes of CSS 2 ([CSS2], section 5.11.3). This allows users to modify content focus presentation with user style sheets. + Refer to the section on frame techniques. The following image shows how Opera [OPERA] uses a solid line border to indicate content focus: Example of a solid line border used to indicate the content focus in Opera 3.60 The following image shows how the Accessible Web Browser [[AWB] uses the system highlight colors to indicate content focus: Example of system highlight colors used to indicate the content focus by the accessible browser project __________________________________________________________ 8.6 Make available to the user an "outline" view of content, built from structural elements (e.g., frames, headers, lists, forms, tables, etc.). [Priority 2] (Checkpoint 8.6) For example, for each frame in a frameset, provide a table of contents composed of headers where each entry in the table of contents links to the header in the document. Note. The outline view does not have to be navigable, but if it is, it may satisfy checkpoint 7.6. Techniques: + For documents that do not use structure properly, user agents may try to create an outline from presentation elements used (insufficiently) to convey structure. + Allow the user to expand or shrink portions of the outline view (configure detail level) for faster access to important parts of content. + Implement a structured view by hiding portions of the document tree by using the CSS 'display' and 'visibility' properties ([CSS2], sections 9.2.5 and 11.2, respectively). + Provide a structured view of form controls (e.g., those grouped by LEGEND or OPTGROUP in HTML) along with their labels. + Refer to structured navigation techniques for checkpoint 7.6. + Refer to the section on list techniques. The following image shows the table of contents view provided by Amaya [AMAYA]. This view is synchronized with the "primary" view so that users may navigate in one view and the focus follows in the other. An entry in the table of contents with a target icon means that the header in the document has an associated anchor. Amaya table of contents view __________________________________________________________ 8.7 Provide a mechanism for highlighting and identifying active elements (through a standard interface where available). [Priority 2] (Checkpoint 8.7) Note. User agents may satisfy this checkpoint by implementing the appropriate style sheet mechanisms, such as link highlighting. Techniques: + Allow users to configure highlighting preferences. + Do not rely on color alone to identify active elements. + Support the ':hover', ':active', and ':focus' pseudo-classes of CSS 2 ([CSS2], section 5.11.3). + Support CSS attribute selectors to match elements with associated scripts ([CSS2], section 5.8). __________________________________________________________ 8.8 Allow the user to configure the outline view. [Priority 3] (Checkpoint 8.8) For example, allow the user to configure the level of detail of the outline. Refer also to checkpoint 8.6. Refer also to checkpoint 5.5. Techniques: + The CSS 'display' and 'visibility' properties ([CSS2], sections 9.2.5 and 11.2, respectively), allow the user to override the default settings in user style sheets. Example. The following CSS 2 style sheet will turn the display off of all HTML elements inside the BODY element except header elements: Another approach would be to use class selectors to identify those elements to hide or display. End example. __________________________________________________________ 8.9 Allow the user to configure what information about links to present. [Priority 3] (Checkpoint 8.9) Note. Do not use color as the only distinguishing factor between visited and unvisited links as some users may not perceive colors and some devices may not render them. Refer also to checkpoint 8.4. Techniques: + Allow configuration through style sheets. Refer to the section on generated content techniques. __________________________________________________________ Guideline 9. Notify the user of content and viewport changes. Checkpoints for user interface accessibility: 9.1 Ensure that when the selection or content focus changes, it is in a viewport after the change. [Priority 2] (Checkpoint 9.1) For example, users navigating links may navigate to a portion of the document outside the viewport, so the viewport should scroll to include the new location of the focus. Techniques: + There are times when the content focus changes (e.g., link navigation) and the viewport must be moved to track it. There are other times when the viewport changes position (e.g., scrolling) and the content focus is moved to follow it. In both cases, the focus (or selection) is in the viewport after the change. + If a search causes the selection or focus to change, ensure that the found content is not hidden by the search prompt. + When the content focus changes, register the newly focused element in the navigation sequence; sequential navigation should start from there. + Unless viewports have been synchronized explicitly, changes to selection or focus in one viewport should not affect the selection or focus in another viewport. __________________________________________________________ 9.2 Prompt the user to confirm any form submission triggered indirectly, that is by any means other than the user activating an explicit form submit control. [Priority 2] (Checkpoint 9.2) For example, do not submit a form automatically when a menu option is selected, when all fields of a form have been filled out, or when a mouseover event occurs. Techniques: + Allow the user to configure script-based submission (e.g., triggered by an "onChange" event). For instance, allow these settings: 1. Do not allow script-based submission. 2. Allow script-based submission after confirmation from the user. 3. Allow script-based submission without confirmation from the user. + Users who navigate a document serially may think that the submit button in a form is the "last" control they need to complete before submitting the form. Therefore, for forms in which additional controls follow a submit button, if those controls have not been completed, inform the user and ask for confirmation (or completion) before submission. __________________________________________________________ 9.3 Allow the user to configure notification preferences for common types of content and viewport changes. [Priority 3] (Checkpoint 9.3) For example, allow the user to choose to be notified (or not) that a script has been executed, that a new viewport has been opened, that a pulldown menu has been opened, that a new frame has received focus, etc. Techniques: + Refer to the section on frame techniques + Allow the user to specify an element type for which notification should be disabled (e.g., TABLE, BODY, and IMG in HTML). + Allow the user to disable notification of changes to CSS properties. + Allow the user to disable notification of images that are changed (e.g., animations composed of a sequence of images). __________________________________________________________ 9.4 When loading content (e.g., document, image, audio, video, etc.) indicate what portion of the content has loaded and whether loading has stalled. [Priority 3] (Checkpoint 9.4) Techniques: + Indicate when loading has finished, for example with a percentage indication or a special message. + Provide status information in a device-independent manner. Use text and non-text status indicators. + Provide this information automatically and allow users to query the viewport for it (e.g., through a menu or keyboard shortcut). + Allow users to configure when to render status information so that assistive technologies may announce changes in status at appropriate times. For instance, allow the user to hide the status bar in order to hide a text rendering. + Allow users to configure what status information they want rendered. Useful status information includes: o Document proportions (numbers of lines, pages, width, etc.) o Number of elements of a particular type (e.g., tables) o The viewport is at the beginning or end of the document. o Size of document in bytes. __________________________________________________________ 9.5 Indicate the relative position of the viewport in rendered content (e.g., the percentage of an audio or video clip that has been played, the percentage of a Web page that has been viewed, etc.). [Priority 3] (Checkpoint 9.5) Note. The user agent may calculate the percentage according to content focus position, selection position, or viewport position, depending on how the user has been browsing. Techniques: + Provide a scrollbar for the viewport. + Indicate the size of the document, so that users may decide whether to download for offline viewing. For example, the playing time of an audio file could be stated in terms of hours, minutes, and seconds. The size of a primarily text-based Web page might be stated in both kilobytes and screens, where a screen of information is calculated based on the current dimensions of the viewport. + Indicate the number of screens of information, based on the current dimensions of the viewport (e.g., "screen 4 of 10"). + Use a variable pitch audio signals to indicate the viewport's different positions. + Provide standard markers for specific percentages through the document. + Provide markers for positions relative to some position - a user selected point, the bottom, the H1, etc. + Put a marker on the scrollbar, or a highlight at the bottom of the page while scrolling (so you can see what was the bottom before you started scrolling. __________________________________________________________ Guideline 10. Allow configuration and customization. Checkpoints for user interface accessibility: 10.1 Provide information to the user about current user preferences for input configurations (e.g., keyboard or voice bindings). [Priority 1] (Checkpoint 10.1) Techniques: + Refer to input configuration techniques. __________________________________________________________ 10.2 Avoid default input configurations that interfere with operating system accessibility conventions. [Priority 1] (Checkpoint 10.2) In particular, default configurations should not interfere with the mobility access keyboard modifiers reserved for the operating system. Refer also to guideline 5. Techniques: + The default configuration should not include "Alt-F4", "Control-Alt-Delete", or other combinations that have reserved meanings on a given operating system. + Clearly document any default configurations that depart from system conventions. + Some reserved keyboard shortcuts are listed in the appendix on accessibility features of some operating systems. __________________________________________________________ 10.3 Provide information to the user about current author-specified input configurations (e.g., keyboard bindings specified in content such as by "accesskey" in HTML). [Priority 2] (Checkpoint 10.3) Techniques: + Refer to input configuration techniques. + Provide information about which keys activate form controls. __________________________________________________________ 10.4 Allow the user to change the input configuration. [Priority 2] (Checkpoint 10.4) For voice-activated browsers, allow the user to modify which voice commands activate functionalities. Similarly, allow the user to modify the graphical user agent user interface for quick access to commonly used functionalities (e.g., through buttons). Refer also to checkpoint 10.5 and checkpoint 10.9. Techniques: + Allow users to restore easily the default input configuration. + When using a physical keyboard, some users require single-key access (refer to checkpoint 10.5), others require that keys activated in combination be physically close together, while others require that they be spaced physically far apart. + Allow users to select from among pre-packaged configurations, to override some of the chosen configuration, and to save it as a profile. Not only will the user save time configuring the user agent, but this will reduce questions to technical support personnel. + Do not allow the user to override important user agent or operating system configurations (e.g., to quit the user agent, or reconfigure it). Refer to input configuration techniques. + Allow users to create macros and bind them to keystrokes or other input methods. __________________________________________________________ 10.5 Allow the user to configure the user agent so that the user's preferred one-step operations may be activated with a single input command (keystroke, voice command, etc.). [Priority 2] (Checkpoint 10.5) Note. User agents are not required to provide single command activation of all user agent functionalities at once, only some of them. This checkpoint is an important special case of checkpoint 10.4. Techniques: + Many people benefit from "single stroke", direct access to important user agent functionalities (e.g., via a single key stroke or voice command): users with poor physical control (who might mistakenly repeat a key stroke), users who fatigue easily (for whom key combinations involve significant effort), users who cannot remember key combinations, and any user who wants to operate the user agent quickly. + Opera [OPERA] includes a mode in which users can access important user agent functionalities with single strokes from the numeric keypad. + Mouse Keys (available on some operating systems) allow users to simulate the mouse through the keyboard. They provide a usable command structure without interfering with the user interface for users who do not require keyboard-only and single-key access. __________________________________________________________ 10.6 Follow operating system conventions to indicate the input configuration. [Priority 2] (Checkpoint 10.6) For example, on some operating systems, if a functionality is available from a menu, the letter of the key that will activate that functionality is underlined. Note. This checkpoint is an important special case of checkpoint 5.9. Techniques: + Use system conventions to indicate the current configuration (e.g., in menus, indicate what key strokes will activate the functionality, underline single keys that will work in conjunction with a trigger key such as Alt, etc.) These are conventions used by the Sun Java Foundations Classes [JAVA-TUT] and Microsoft Foundations Classes for Windows. + Ensure that information about changes to the input configuration is available in a device-independent manner (e.g., through visual and audio cues, and through text). + If the currently active configuration changes locally (e.g., a search prompt opens, changing the keyboard mapping for the duration of the prompt), alert the user. + Named configurations are easier to remember. This is especially important for persons with certain types of cognitive disabilities. For example, if the invocation of a search prompt changes the input configuration, the user may remember more easily which keystrokes are active in search mode if alerted that there is a "Search Mode". Context-sensitive help (if available) should reflect the change in mode, and a list of keybindings for the current mode should be readily available to the user. __________________________________________________________ 10.7 For the configuration requirements of this document, allow the user to save user preferences a profile. [Priority 2] (Checkpoint 10.7) Note. This includes user preferences for styles, presentation rates, input configurations, navigation, views, and notification. Users must be able to select from among available profiles or no profile (i.e., the user agent default settings). Techniques: + Follow applicable operating system conventions for input configuration profiles. + Allow users to choose a different profile, to switch rapidly between profiles, and to return to the default input configuration. __________________________________________________________ 10.8 Ensure that frequently used functionalities are easily activated in the default input configuration. [Priority 3] (Checkpoint 10.8) Make the most frequent operations easy to access and operable through a single command. Techniques: + Provide different input configuration profiles (e.g., one keyboard profile with key combinations close together and another with key combinations far apart). + Test the default keyboard configuration for usability. Ask users with different disabilities and combinations of disabilities to test configurations. + Provide convenient bindings to functionalities that promote accessibility such as navigation of links. + Provide convenient bindings for controlling the user interface, such as showing, hiding, moving, and resizing graphical viewports. + For people using one hand, a few fingers, or a headwand pointer, access to important functionalities must be available through one or at most two key strokes. + Consider distance between keys and key alignment (e.g., "9/I/K", which align almost vertically on many keyboards) in the default configuration. For instance, if Enter is used to active links, put other link navigation commands near it (e.g., page up/down, arrow keys, etc. on many keyboards). In configurations for users with reduced mobility, pair related functionalities on the keyboard (e.g., left and right arrows for forward and back navigation). + Allow users to accomplish tasks through repeated keystrokes (e.g., sequential navigation) since this means less physical repositioning for all users. However, repeated keystrokes may not be efficient for some tasks. For instance, do not require the user to position the pointing device by pressing the "down arrow" key repeatedly. + So that users do not mistakenly activate certain functionalities, make certain combinations "more difficult" to invoke (e.g., users are not likely to press Control-Alt-Delete accidentally). + Avoid deeply nested graphical menus. + Input configurations should allow quick and direct navigation that does not rely on graphical output. Do not require the user to navigate through "space" (through a graphical user interface) as the only way to activate a functionality. + Offer a mode that makes the input configuration compatible with other versions of the software (or with other software). + Refer also to checkpoint 10.6. __________________________________________________________ 10.9 Allow the user to configure the arrangement of graphical user agent user interface controls. [Priority 3] (Checkpoint 10.9) Note. This checkpoint is an important special case of checkpoint 10.4. Techniques: + Allow multiple icon sizes (big, small, other sizes). + Allow the user to choose icons and/or text. + Allow the user to change the grouping of icons. + Allow the user to show and hide controls. This benefits users with cognitive disabilities and users navigate user interface controls sequentially. + Allow the user to change the position of control bars, icons, etc. Do not rely solely on drag-and-drop for reordering tool bar. Allow the user to configure the user agent user interface in a device-independent manner (e.g., through a text-based profile). __________________________________________________________ Guideline 11. Provide accessible product documentation and help. Checkpoints for user interface accessibility: 11.1 Provide a version of the product documentation that conforms to the Web Content Accessibility Guidelines 1.0 [WCAG10]. [Priority 1] (Checkpoint 11.1) User agents may provide documentation in many formats, but at least one must conform to the Web Content Accessibility Guidelines 1.0 [WCAG10]. Techniques: + Distribute accessible documentation over the Web, on CD-ROM, or by telephone. Alternative hardcopy formats may also benefit some users. + Web-based support and/or documentation that is produced or maintained by the manufacturer of a user agent or by a sub-contractor of the user agent's developer must conform to the Web Content Accessibility Guidelines 1.0 [WCAG10]. In particular: 1. Provide text equivalents of all non-text content (e.g., graphics, audio presentations, etc.); 2. Provide extended descriptions of screen-shots, flow charts, etc.; 3. Use clear and consistent navigation and search mechanisms; 4. Use the NOFRAMES element when the support/documentation is presented in a FRAMESET; 5. Refer also to checkpoint 11.3. + Describe the user interface with device-independent terms. For example, use "select" instead of "click on". + Provide documentation in small chunks (for rapid downloads) and also as a single source (for easy download and/or printing). A single source might be a single HTML file or a zip archive of several HTML documents and included images. + Ensure that run-time help and any Web-based help or support information is accessible and may be operated with a single, well-documented, input command (e.g., key stroke). Use operating system conventions for input configurations related to run-time help. + Provide documentation in alternative formats such as Braille (refer to "Braille Formats: Principles of Print to Braille Transcription 1997" [BRAILLEFORMATS]), large print, or audio tape. Agencies such as Recording for the Blind and Dyslexic [RFBD] and the National Braille Press [NBP] can create alternative formats. + Provide accessible documentation for all audiences: end users, developers, etc. For instance, developers with disabilities may wish to add accessibility features to the user agent, and so require information on available APIs and other implementation details. + Ensure that product identification codes are accessible to users so they may install their software. Codes printed on product cases will not be accessible to people with visual disabilities. __________________________________________________________ 11.2 Document all user agent features that promote accessibility. [Priority 1] (Checkpoint 11.2) For example, review the documentation or help system to ensure that it includes information about the accessibility features discussed in this document. Techniques: + Refer also to techniques for checkpoint 11.4. + Provide a sensible index to accessibility features. For instance, users should be able to find "How to turn off blinking text" in the documentation. The user agent may implement this feature by turning off scripts, but users should not have to guess (or know) that turning off scripts will turn off blinking text. Controls available through the user interface should also present these features with the proper level of abstraction. + Document configurable features in addition to defaults for those features. + Document the features implemented to conform with these guidelines. + Include references to accessibility features in both the table of contents and index of the documentation. __________________________________________________________ 11.3 Document the default input configuration (e.g., default keyboard bindings). [Priority 1] (Checkpoint 11.3) Techniques: The following table shows how one might document keyboard bindings. It show the default keyboard configuration for versions of Navigator [NAVIGATOR] running on the Macintosh, Unix, and Windows operating systems. If a function exists in the browser but does not have a shortcut, its corresponding cell is marked with an asterisk (*). If the function does not exist, it is left blank. Note. This table lists some, but not all, functionalities and keyboard shortcuts of Navigator. It is meant to illustrate, not serve as definitive documentation. Some entries contain links to special notes. The number in parentheses following the link is the number of the relevant note. Note. To make this table accessible, a linear version of Navigator Keyboard Shortcuts is available. CAPTION: Navigator Keyboard Shortcuts Function Macintosh (v 4.61) Unix (v 4.51) Windows (v 4.7) Move within a document Scroll to next page Page Down Page Down Page Down Scroll to previous page Page Up Page Up Page Up Scroll to top * * Control-Home Scroll to bottom * * Control-End Move between documents Open a new document Command+L Alt+O Control+O Stop loading a document Command+. Esc Esc Refresh a document Command+R Alt+R Control+R Load previous document Command+[ or Command+Left Arrow Alt+Left Arrow Alt+Left Arrow Load next document Command+] or Command+Right Arrow Alt+Right Arrow Alt+Right Arrow Navigate elements within a document Move focus to next frame * * * Move focus to previous frame * * * Move focus to next active element (1) Tab Tab Tab Move focus to previous active element (1) Shift+Tab Shift+Tab Shift+Tab Find word in page Command+F Alt+F Control+F Act on HTML elements Select a link * * Enter Toggle a check box * * Shift or Enter Activate radio button * * Shift Move focus to next item in an option box * * Down Arrow or Right Arrow Move focus to previous item in an option box * * Up Arrow or Left Arrow Select item in an option box * * Enter Press a button (2) Return Enter Enter Navigate menus Activate menu * * Alt+ the underlined letter in the menu title Deactivate menu * Esc Esc Move focus to next menu item * * (3) Down Arrow Move focus to previous menu item * * (3) Up Arrow Select menu item * underlined letter in the menu item Enter Move focus to submenu * * (3) Right Arrow Move focus to main menu * * (3) Left Arrow Navigate bookmarks View bookmarks menu * (4) * Alt+C+B Move focus to next item in bookmarks menu Down Arrow (4) * Down Arrow Move focus to previous item in bookmarks menu Up Arrow (4) * Up Arrow Select item in bookmarks menu Return (4) * Enter Add bookmark Command+D Alt+K Control+D Edit bookmarks Command+B Alt+B Control+B Delete current bookmark (5) Delete Alt+D Delete Navigate history list View history list Command+H Alt+H Control+H Move focus to next item in history list * * Down Arrow Move focus to previous item in history list * * Up Arrow Move focus to first item in history list * * Left Arrow Select item in history list * * Enter (6) Close history list Command+W Alt+W Control+W Define view Increase font size (7) Shift+Command+] Alt+] Control+] Decrease font size (7) Shift+Command+[ Alt+[ Control+[ Change font color * * * Change background color * * * Turn off author-defined style sheets * * * Turn on user-defined style sheets (8) ? ? ? Apply next user-defined style sheet ? ? ? Apply previous user-defined style sheet ? ? ? Other functionalities Access to documentation * * * Notes. 1. In Windows, active elements of the user interface include links, text entry boxes, buttons, checkboxes, radio buttons, etc. In Unix and Macintosh, Tab cycles through text entry boxes only. 2. In Windows, this works for any button, since any button can gain the user interface focus using keyboard commands. In Unix and Macintosh, this only applies to the "Submit" button following a text entry. 3. In Unix, the menus cannot be opened with shortcut keys. However, once a menu is opened it stays opened until it is explicitly closed, which means that the menus can still be used with shortcut keys to some extent. Sometimes left and right arrows move between menus and up and down arrows move within menus, but this does not seem to work consistently, even within a single session. 4. In Macintosh, you cannot explicitly view the bookmarks menu. However, if you choose "Edit Bookmarks", which does have a keyboard shortcut, you can then navigate through the bookmarks and open bookmarked documents in the current window. 5. To delete a bookmark you must first choose "Edit Bookmarks" and then move the focus to the bookmark you want to delete. 6. In Windows, when you open a link from the history menu using Enter, the document opens in a new window. 7. All three systems have menu items (and corresponding shortcut keys) meant to allow the user to change the font size. However, the menu items are consistently inactive in both Macintosh and Unix. The user seems to be able to actually change the font sizes only in Windows. 8. It is important to allow users to set their own Cascading Style Sheets. Although Navigator does currently allow the user to override the author's choice of foreground color, background color, font, and font size, it does not allow some of the advanced capabilities that make CSS so powerful. For example, a blind user may want to save a series of style sheets which show only headers, only links, etc., and then view the same page using some or all of these style sheets in order to orient himself to the contents and organization of the page before reading any of the actual content. __________________________________________________________ 11.4 In a dedicated section of the documentation, describe all features of the user agent that promote accessibility. [Priority 2] (Checkpoint 11.4) Note. This is a more specific requirement than checkpoint 11.2. Techniques: + Integrate information about accessibility features throughout the documentation. The dedicated section on accessibility should provide access to the documentation as a whole rather than standing alone as an independent section. For instance, in a hypertext-based help system, the section on accessibility should link to pertinent topics elsewhere in the documentation. + Ensure that the section on accessibility features is easy to find. __________________________________________________________ 11.5 Document changes between software releases. [Priority 2] (Checkpoint 11.5) Techniques: + At a minimum provide a text description of changes (e.g., in a README file). + In particular, document changes to the user interface. __________________________________________________________ 3 Accessibility topics This section presents general accessibility techniques that may apply to more than one checkpoint. 3.1 Access to content User agents must ensure that users have access to content, either rendered through the user interface or made available to assistive technologies through an API. While providing serial access to a stream of content would satisfy this requirement, this would be analogous to offering recorded music on a cassette: other technologies exist (e.g., CD-ROMs) that allow direct access to music. It is just as important for user agents to allow users to access Web content efficiently, whether the content is being rendered as a two-dimensional graphical layout, an audio stream, or a line-by-line Braille stream). Providing efficient access to content involves: * Preserving structure when rendering * Allowing the user to select specific content and query its structure or context * Providing access to equivalent alternatives of content. * Using and generating metadata to provide context These topics are addressed below. 3.1.1 Preserve and provide structure When used properly, markup languages structure content in ways that allow user agents to communicate that structure across different renderings. A table describes relationships among cells and headers. Graphically, user agents generally render tables as a two-dimensional grid. However, serial renderings (e.g., speech and Braille) must also make those relationships apparent, otherwise users will not understand the purpose of the table and the relationships among its cells (refer to the section on table techniques). User agents must render content in ways that allow users to understand the underlying document structure, which may consist of headers, lists, tables, synchronized multimedia, link relationships, etc. Providing alternative renderings (e.g., an outline view) will also help users understand document structure. Note. Even though the structure of a language like HTML is defined by a Document Type Definition (DTD), user agents may convey structure according to a "more intelligent" document model when that model is well-known. For instance, in the HTML DTD, header elements do not nest, but presenting the document as nested headers may be convey the document's structure more effectively than as a flat list of headers. 3.1.2 Allow access to selected content The guidelines emphasize the importance of navigation as a way to provide efficient access to content. Navigation allows users to access content more quickly and when used in conjunction with selection and focus mechanisms, allows users to query content for metadata. For instance, blind users often navigate a document by skipping from link to link, deciding whether to follow each link based on metadata about the link. User agents can help them decided whether to follow a link by allowing them to query each focused link for the link text, title information, information about whether the link has been visited, whether the link involves a fee, etc. While much of this information may be rendered, the information must also be available to assistive technologies. For example, the Amaya browser/editor [AMAYA] makes available all attributes and their values to the user through a context menu. The user selects an element (e.g., with the mouse) and opens an attribute menu that changes according to the selected element. The selection may be widened (moved to the nearest node one level up the document tree) by pressing the Escape key; this is a form of structured navigation based on the underlying document object model. Information about attributes is also available through Amaya's structured view, which renders the document tree as structured text. Users may want to select content based on structure alone (as offered by Amaya) but also based on how the content has been rendered. For instance, most user agents allow users to select ranges of text content that may cross "element boundaries". 3.1.3 Access to equivalent alternatives of content Authors provide equivalent alternatives to content so that users may understand the function of a page or part of a page even though they may not be able to make use of a particular content type. For example, authors must provide text equivalents for non-text content (e.g., images, video, audio presentations, etc.) because text may be rendered as speech or Braille and may be used by users with visual or hearing or both disabilities. User agents must ensure that these alternatives are available to users, either through the user interface or through an API. How authors specify equivalent alternatives depends on the markup language used. For information about equivalent alternatives for SMIL [SMIL] content, refer to "Accessibility Features of SMIL" [SMIL-ACCESS]. In HTML 4.01 [HTML4], authors supply equivalent alternatives for content as follows: * For the IMG element (section 13.2): The "alt" (section 13.8), "title" (section 7.4.3), and "longdesc" (section 13.2) attributes. Refer to the section on long descriptions. * For the OBJECT element (section 13.3): The content of the element and the "title" attribute. * For the deprecated APPLET element (section 13.4): The "alt" attribute and the content of the element. * For the AREA element (section 13.6.1): The "alt" attribute. * For the INPUT element (section 17.4): The "alt" attribute. * For the ACRONYM and ABBR elements (section 9.2.1): The "title" attribute may be used for the acronym or abbreviation expansion. * For the TABLE element (section 11.2.1), the "summary" attribute. * For frames, the NOFRAMES element (section 16.4.1) and the "longdesc" attribute (section 16.2.2) on FRAME and IFRAME (section 16.5). * For scripts, the NOSCRIPT element (section 18.3.1). Techniques for providing access to equivalent alternatives include the following: * Make information available with different levels of detail. For example, for a voice browser, offer two options for equivalent alternatives to HTML images: 1. Speak only "alt" text by default, but allow the user to hear "longdesc" text on an image by image basis. 2. Speak "alt" text and "longdesc" for all images. * Allow the user to configure how the user agent renders a long description (e.g., "longdesc" in HTML 4.01 [HTML4]). Some possibilities include: 1. Render the long description in a separate view. 2. Render the long description in place of the associated element. 3. Do not render the long description, but allow the user to query whether an element has an associated long description (e.g., with a context-sensitive menu) and provide access to it. 4. Use an icon (with a text equivalent) to indicate the presence of a long description. 5. Use an audio cue to indicate the presence of a long description when the user navigates to the element. * For an object with a preferred geometry (e.g., an image) that is not rendered, allow the user to configure how the equivalent alternative should be rendered. For example, within the preferred geometry, by ignoring the author-specified geometry altogether, etc. * For multimedia presentations with several alternative tracks, ensure access to all tracks and allow the user to select individual tracks. The Quicktime player [QUICKTIME] allows users to turn on and off any number of tracks separately. * For multimedia presentations with several alternative tracks, allow users to select tracks based on natural language preferences. SMIL 1.0 [SMIL] allows users to specify captions in different natural languages. By setting language preferences in the SMIL player (e.g., the G2 player [G2]), users may access captions (or audio) in different languages. Allow users to specify different languages for different content types (e.g., English audio and Spanish captions). * For missing equivalent alternatives of content: + The "Altifier Tool" [ALTIFIER] illustrates smart techniques for generating text equivalents for images, etc., when the author hasn't supplied any. + If no captioning information is available and captioning is turned on, render "no captioning information available" in the captioning region of the viewport. 3.1.4 Context Authors and user agents provide context to users through content, structure, navigation mechanisms, and query mechanisms. Titles, dimensions, dates, relationships, the number of elements, and other metadata all help orient the user, particularly when available as text. For instance, user agents can help orient users by allowing them to request that document headers and lists be numbered. Refer also to the section on table techniques, which explains how users agents can offer table navigation and the ability to query a table cell for information about the cell's row and column position, associated header information, etc. * User agents can use style sheet languages such as CSS 2 [CSS2] and XSLT [XSLT] to generate context information (refer to techniques for generated content). * For information about elements and attributes that convey metadata in HTML, refer to the index of elements and attributes in "Techniques for Web Content Accessibility Guidelines 1.0" [WCAG10-TECHS]. * For information about elements and attributes that convey metadata in SMIL, refer to the index of attributes in the W3C Note "Accessibility Features of SMIL" [SMIL-ACCESS]. * Describe a selected element's position within larger structures (e.g., numerical or relative position in a document, table, list, etc.). For example: tenth link of fifty links; document header 3.4; list one of two, item 4.5; third table, three rows and four columns; current cell in third row, fourth column; etc. Allow users to get this information on demand (e.g., through a keyboard shortcut). Provide this information on the status line on demand from the user. 3.2 User control of style To ensure accessibility, users must be able to configure the style of rendered content and the user interface. Author-specified styles, while important, may make content inaccessible to some users. User agents must allow users to increase the size of text (e.g., with a zoom mechanism or font size control), to change colors and color combinations, to slow down multimedia presentations, etc. To give authors design flexibility and allow users to control important aspects of content style, user agents should implement CSS ([CSS1], [CSS2]) and allow users to create and apply user style sheets. CSS includes mechanisms for tailoring rendering for a particular output medium, including audio, Braille (fixed and refreshable), screen, and print. * User agents should implement the cascade order of CSS 2 ([CSS2], section 6.4.1) not CSS 1. In CSS 2, user style sheets with "!important" (section 6.4.2) take precedence over author styles. Refer also to Web Content Accessibility Guidelines 1.0 checkpoint 3.3 [WCAG10]. * CSS-enabled user agents should take into account markup used for style into the cascade, giving it a lower weight than actual style sheets. This allows authors to specify style through markup for older user agents and to use more powerful style sheets for CSS-enabled user agents. Refer to the section on the precedence of non-CSS presentational hints in CSS 2 ([CSS2], section 6.4.4). * To hide the CSS syntax from the user, user agents may implement user style sheets through the user agent user interface. User agents can generate a user style sheet from user preferences or behave as though it did. Amaya [AMAYA] provides a GUI-based interface to create and apply internal style sheets. The same technique may be used to control a user style sheet. * For animations rendered natively, allow users to control the rate of animation, to pause and play animations, to step through the animation, and to play it at the specified rate. When an animation is synchronized with audio, the user may need to play the animation separately from the associated audio. * Allow the user to pause a video presentation, to move, resize, and position tracks that appear on the screen (including captions, subtitles and signed translations) and to apply CSS stylesheets to text-based presentation. * In the user interface: + Allow the user to select large or small buttons and controls. Ensure that these values are applied consistently across the user interface. + Allow the user to regroup buttons and controls, and reorder menus. + Use standard operating system controls for allowing configuration of font sizes, speech rates, and other style parameters. 3.3 Link techniques User agents make links accessible by providing navigation to links, helping users decide whether to follow them, and allowing interaction in a device-independent manner. Link techniques include the following: * Refer to sequential navigation techniques for information about navigating to links. * Provide a link view that lists all links in the document. Allow the user to configure how the links are sorted (e.g., by document order, sequential navigation order alphabetical order, visited or unvisited or both, internal or external or both, etc.). * Help the user remember links by including metadata in the link view. For example, identify a selected link as "Link X of Y", where "Y" is the total number of links. Lynx [LYNX] numbers each link and provides information about the relative position in the document. Position is relative to the current page and the number of the current page out of all pages. Each page usually has 24 lines. * Allow the user to configure how much information about a link to present in the content view (when a link receives focus). For instance, allow the user to choose between "Display links using hyperlink text" or "Display links by title (if present)", with an option to toggle between the two views. For a link without a title, use the link text. * For links with non-text content such as images, make available a text equivalent as follows: 1. If the author has specified a non-empty text equivalent for the image (e.g., "alt" in HTML), use that as the link text; 2. Otherwise, use the link title if available; 3. Otherwise, use title information of the designated resource (e.g., the TITLE element of HTML for links to HTML documents). 4. Otherwise, render part of the filename or URI of the designated resource. 5. Otherwise, insert a generic placeholder (e.g., [LINK]) in place of the image. * For an image in link content, ensure that the user has access to the link and any long description associated with the image. * Ensure that all information about a link is available in a device-independent manner. For example, do not rely solely on fonts or colors to alert the user whether or not the link has previously been followed. Allow the user to configure how information will be presented (colors, sounds, status bar messages, some combination, etc.). * If the user activates a broken link, leave the viewport where it is and alert the user (e.g., in the status bar, with graphical or aural icons, etc.). Moving the viewport suggests that a link is not broken, which may disorient the user. * If the focus is used to select active elements, support the ':hover', ':active', and ':focus' pseudo-classes of CSS 2 ([CSS2], section 5.11.3). This allows users to modify content focus presentation with user style sheets. Use them in conjunction with the CSS 2 ':before' pseudo-elements ([CSS2], section 5.12.3) to clearly indicate that something is a link (e.g., 'A:before { content : "LINK:" }'). Refer also to techniques for generated content. * Do not consider that all local links (to anchors in the same page) have been visited when the page has been visited. Jaws for Windows [JFW] offers a view for configuring a number of rendering features, notably some concerning link types, text link verbosity, image map link verbosity, graphical link verbosity, and internal links: Jaws for Windows HTML Options menu, which allows configuration of a number of link rendering options 3.4 List techniques User agents can make lists accessible by ensuring that list structure - and in particular, embedded list structure - is available through navigation and rendering. * Allow users to turn on "contextual" rendering of lists (even for unordered "bullet" lists). Use compound numbers (or letters, numbers, etc.) to introduce each list item (e.g., "1, 1.1, 1.2, 1.2.1, 1.3, 2, 2.1"). This provides more context and does not rely on the information conveyed by a graphical rendering, as in: 1. 1. 2. 1. 3. 2. 1. which might be serialized for speech or Braille as "1, 1, 2, 1, 2, 3, 2, 1". * Specify list numbering styles in CSS. Refer to the section generated content, automatic numbering, and lists in CSS ([CSS2], section 12). Example. The following CSS 2 style sheet (taken from CSS 2, section 12.5) shows how to specify compound numbers for nested lists created with either UL or OL elements. Items are numbered as "1", "1.1", "1.1.1", etc. End example. 3.5 Table techniques The HTML TABLE element was designed represent relationships among data ("data" tables). Even when authored well and used according to specification, tables may pose problems for users with disabilities for a number of reasons: * Users who access a table serially (e.g., as speech or Braille) may have difficulty grasping the relationships among cells, especially for large and complex tables. * Users who with cognitive disabilities may have trouble grasping or remembering relationships between cells and headers, especially for large and complex tables. * Users of screen magnifiers or with physical disabilities may have difficulties navigating to the desired cells of a table. For both of these situations, user agents may assist these users by providing table navigation mechanisms and supplying context that is present in a two-dimensional rendering (e.g., the cells surrounding a given cell). To complicate matters, many authors use tables to lay out Web content ("layout" tables). Not only are table structures used to lay out objects on the screen, table elements such as TH (table header) in HTML are used to font styling rather than to indicate a true table header. These practices make it difficult for assistive technologies to rely on markup to convey document structure. Consequently, assistive technologies often must resort to interpreting the rendered content, even though the rendered content has "lost" information encoded in the markup. For instance, when an assistive technology "reads" a table is from its graphical rendering, the contents of multiline cells may become intermingled. For example, consider the following table: This is the top left cell This is the top right cell of the table. of the table. This is the bottom left This is the bottom right cell of the table. cell of the table. Screen readers that read rendered content line by line would read the table cells incorrectly as "This is the top left cell This is the top right cell". So that assistive technologies are not required to gather incomplete information from renderings, these guidelines require that user agents provide access to document source through an API (refer to checkpoint 5.3). The following sections discuss techniques for providing improved access to tables. 3.5.1 Table metadata Users of screen readers or other serial access devices cannot gather information "at a glance" about a two-dimensional table. User agents can make tables more accessible by providing the user with table metadata such as the following: * The table caption (the CAPTION element in HTML) or summary information (the "summary" attribute in HTML). * The number of column groups and columns. * The number of row groups and rows, in particular information about table headers and footers. * Note that the number of columns may change according to the row. * Some parts of a table may have two dimensions, others three, others four, etc. Project dimensionality higher than two onto two when rendering information. * Which rows contain header information (whether at the top or bottom of the table). * Which columns contain header information (whether at the left or right of the table). * Whether there are subheads. * How many rows or columns a header spans. When navigating, quick access to table metadata will allow users to decide whether to navigate within the table or skip over it. Other techniques: * Allow users to query table summary information from inside a cell. * Provide different levels of detail (e.g., brief table summary and a more detailed summary). * Allow the user to configure navigation so that table metadata is not (re-)rendered each time the user enters the table. 3.5.2 Linear rendering of tables A linear rendering of tables -- cells presented one at a time, row by row or column by column -- may be useful, but generally only for simple tables. For more complex tables, user agents need to convey more information about relationships among cells and their headers. Note. The following techniques apply to columns as well as rows. The elements listed in this section are HTML 4.01 table elements ([HTML4], section 11). * Provide access to one row at a time, beginning with any column header. If a header is associated with more than one row, offer that header for each row concerned. * Render cells with their associated headers. Allow the user to configure how often headers are rendered (e.g., by supporting the 'speak-header' property in CSS 2 [CSS2], section 17.7.1). Note also that the "abbr" attribute in HTML 4.01 specifies abbreviated headers for speech and other rendering ([HTML4], section 11.2.6). Refer also to information about cell headers later in this section. * Provide access to cell content as marked up in the document source. * Refer to techniques for authoring accessible tables in "Techniques for Web Content Accessibility Guidelines 1.0" [WCAG10-TECHS]. 3.5.3 Cell rendering The most important aspect of rendering a table cell is that the cell's contents be rendered faithfully and be identifiable as the contents of a single cell. However, user agents may provide additional information to help orient the user: * Render the row and column position of the cell in the table. * Indicate how many rows and columns a cell spans. * Since the contents of a cell in a data table may only be comprehensible in context (i.e., with associated header information, row/column position, neighboring cell information etc.), allow users to navigate to cells and query them for this information. * For HTML tables, refer to the section on associating header information with data cells of HTML 4.01 ([HTML4], section 11.4.1). * In a table with leading row and column of TH cells, the interpretation of the corner cell as an empty TD or TH should not contribute to the set of headings for cells in that row and column. * For nested tables, render information about the level of nesting. * Since a cell may belong to N different dimensions in a multi-dimensional table, provide information about headers from each dimension. 3.5.4 Cell header algorithm Properly constructed data tables distinguish header cells from data cells. How headers are associated with table cells depends on the markup language. The following algorithm is based on the HTML 4.01 algorithm to calculate header information ([HTML4], section 11.4.3). For the sake of brevity, it assumes a left-to-right ordering, but will work for right-to-left tables as well (refer to the "dir" attribute of HTML 4.01 [HTML4], section 8.2). For a given cell: * Search left from the cell's position to find row header (TH) cells. Then search upwards from the cell's position to find column header cells. The search in a given direction stops when the edge of the table is reached or when a data cell is found after a header cell. If no headers are found in either direction (left or up), search in the other directions (right or down). * Allow the user to configure how the header cell contributes the text header: either cell content or the "abbr" attribute value ([HTML4], section 11.2.6). * Insert row headers into the list in the (left-to-right) order they appear in the table. Include values implicitly resulting from header cells in prior rows with rowspan="R", sufficient to extend into the current row. * Insert column headers after row headers, in the (top-to-bottom) order they appear in the table. Include values implicitly resulting from header cells in other columns with colspan="C", sufficient to extend into the current column containing the TD cell. * If a header cell has a value for the "headers" attribute, then insert these into the list and stop the search for the current direction. * Treat cells with a value for the "axis" attribute as header cells. * Be sure to take into account header cells that span several rows or columns. Not all data tables include proper header markup, which the user agent may be able to detect. Some repair strategies for finding header information include the following: * Consider that the top or bottom row contains header information. * Consider that the leftmost or rightmost column in a column group contains header information. * If cells in an edge row or column span more than one row or column, consider the following row or column to contain header information as well. * When trying to guess table structure, present several solutions to the user. Other repair issues to consider: * TH cells on both the left and right of the table need to be considered. * For TH cells with "rowspan" set: the content of those TH cells must be considered for each of the N-1 rows below the one containing that TH content. * An internal TH in a row surrounded on either side by TDs has no means to specify to which (row or column) that TH overrides what existed to its left or above it. * Finding column header cells assumes they are all above the TD cell to which they apply. * A TH with "colspan" set needs to be included in the list of TH for the N-1 columns to the right of the column in which the TH is found. 3.5.5 Table navigation To permit efficient access to tables, user agents should allow users to navigate to tables and within tables, to select individual cells, and to query them for information about the cell and the table as a whole. * Allow users to navigate to a table, down to one of its cells, and back up to the table level. This should work recursively for nested tables. * Allow users to navigate to a cell by its row and column position. * Allow users to navigate to all cells under a given header. * Allow users to navigate row by row or column by column. * Allow users to navigate to the cells around the current cell. * Allow users to navigate to the first or last cell of a row, column, or the table. * Allow users to navigate from a cell directly to its related headers (if it's possible to navigate to the headers). * Allow the user to search for text content within a table (i.e., without searching outside of the table). Allow the user to search for text content within specific rows or columns, row groups or column groups, or limited by associated headers. * Notify the user when the navigation reaches a table edge and when a cell contains another table. * Allow relative and direct navigation. For example, entering "-3, 20" might mean "left three cells, up 20 cells"). * Allow navigation of table headers or footers only. * Consider the issues raised by navigation to or from a cell that spans more than one row or column. * For examples of table navigation, refer to [TABLENAV]. 3.6 Image map techniques One way to make an image map accessible is to render the links it contains as text links. This allows assistive technologies to render the links a speech or Braille, and allows benefits users with slow access to the Web and users of small Web devices that don't support images but can support hypertext. User agents may allow users to toggle back and forth between a graphical mode for image maps and a text mode. To construct a text version of an image map in HTML: * If the content of the MAP element includes links, use these. * Otherwise, for each AREA in the map, if a (non-null) text equivalent is available (the "alt" attribute), use it as the content of a generated link. * When the author has specified a null text equivalent, do not render the link. * When the author has not specified a text equivalent, render (for example) "Map area" followed by part of the URI of the link. Furthermore, user agents that render a text image map instead of an image may preface the text image map with metadata such as: * a string that announces the image map (e.g., "Start map") * any text equivalent associated with the image (e.g., "alt" for IMG). * the number of links in the map. Allow users to suppress shrink and expand text versions of image maps so that they may quickly navigate to an image map (which may be, for example, a navigation tool bar) and decide whether to "expand" it and follow the links of the map. The metadata listed above will allow users to decide whether to expand the map. Ensure that the user can expand and shrink the map and navigate its links using the keyboard and other input devices. 3.7 Frame techniques Frames were originally designed so that authors could divide up graphic real estate and allow the pieces to change independently (e.g., selecting an entry in a table of contents in one frame changes the contents of a second frame). While frames are not inherently inaccessible, they raise some accessibility issues: * Alternatives to frame content. Some users cannot make use of frames because they cannot grasp the (spatial or logical) relationships conveyed by frame layout. Others cannot use them because their user agents or assistive technology does not support them or makes access difficult (e.g., users with screen readers or screen magnifiers). * Navigation. Users must be able to navigate from frame to frame in a device independent manner. * Orientation. Users need to know what frame they are in (thus, frames must be titled), what other frames are available, and how the frames of a frameset are organized. * Dynamic changes. Users need to know how the changes they cause in one frame affect other frames. To name a frame in HTML, use the following algorithm: 1. Use the "title" attribute on FRAME, or if not present, 2. Use the "name" attribute on FRAME, or if not present, 3. Use title information of the referenced frame source (e.g., the TITLE element of the source HTML document), or 4. Use title information of the referenced long description (e.g., what "longdesc" refers to in HTML), or 5. Use frame context (e.g., "Frame 2.1.3" to indicate the path to this frame in nested framesets). To make frames accessible, user agents should do the following: * Make available the author-supplied to frame equivalents (e.g., provided by the HTML 4.01 NOFRAMES element ([HTML4], section 16.4.1). * Notify the user when the viewport contains a frameset. * Render a frameset as a list of links to named frames so the user can identify the number of frames. The list of links may be nested if framesets are nested. * Provide information about the number of frames in the frameset. * Highlight the current frameset (e.g., with a thick border, by displaying the name of the current frameset in the status bar, etc. * Allow the user to query the current frame for metadata about the frame. Make available the frame title for speech synthesizers and Braille displays. Users may also use information about the number of images and words in the frame to guess the purpose of the frame. For example, few images and few words is probably a title, more words is probably an index, many words is probably text area. * Allow navigation between frames (forward and backward through the nested structure, return to global list of links to frames). Note. Recall that the user must be able to navigate frames through all supported input devices. * Allow navigation to frame equivalents. * Allow the user to bookmark the current frame. * Notify the user when an action one frame causes the content of another frame to change. Allow the user to navigate quickly to the frame(s) that changed. * Authors can suppress scrolling of frames with scrolling="no". In this case, the user agent must make available content that is not in the viewport. * The user agent may ignore some attributes of the FRAME element of HTML 4.01 ([HTML4], section 16.2.2): "noresize", "scrolling", and "frameborder". Consider renderings of the following document: Time Value of Money <P>List of Presentation Slides</P> <OL> <LI><A HREF="slide001">Time Value of Money</A> <LI><A HREF="slide002">Topic Overview</A> <LI><A HREF="slide003">Terms and Short Hand</A> <LI><A HREF="slide004">Future Value of a Single CF</A> <LI><A HREF="slide005">Example 1: FV example:The NBA's new Larry Bird exception</A> <LI><A HREF="slide006">FV Example: NBA's Larry Bird Exception (cont.)</A> <LI><A HREF="slide007">SuperStar's Contract Breakdown</A> <LI><A HREF="slide008">Present Value of a Single Cash Flow</A> <LI><A HREF="slide009">Example 2: Paying Jr, and A-Rod</A> <LI><A HREF="slide010">Example 3: Finding Rate of Return or Interest Rate</A> <LI><A HREF="slide011">Annuities</A> <LI><A HREF="slide012">FV of Annuities</A> <LI><A HREF="slide013">PV of Annuities</A> <LI><A HREF="slide014">Example 4: Invest Early in an IRA</A> <LI><A HREF="slide015">Example 4 Solution</A> <LI><A HREF="slide016">Example 5: Lotto Fever </A> <LI><A HREF="slide017">Uneven Cash Flows: Example 6:Fun with the CF function</A> <LI><A HREF="slide018">Example 6 CF worksheet inputs</A> <LI><A HREF="slide019">CF inputs continued</A> <LI><A HREF="slide020">Non-Annual Interest Compounding</A> <LI><A HREF="slide021">Example 7: What rate are you really paying?</A> <LI><A HREF="slide022">Nominal to EAR Calculator</A> <LI><A HREF="slide023">Continuous Interest Compounding</A> <LI><A HREF="slide024">FV and PV with non-annual interest compounding</A> <LI><A HREF="slide025">Non-annual annuities</A> <LI><A HREF="slide026">Example 8: Finding Monthly Mortgage Payment</A> <LI><A HREF="slide027">solution to Example 8</A> </OL> The following examples show how some user agents handle this frameset. First, rendering in Internet Explorer [IE]: Example frameset with five frame panes rendered in Microsoft Internet Explorer 5.0 Rendering by Lynx [LYNX]: Time Value of Money FRAME: Size buttons FRAME: Presentation Outline FRAME: Navigation buttons FRAME: Slide Image FRAME: Notes List of Presentation Slides 1. Time Value of Money 2. Topic Overview 3. Terms and Short Hand 4. Future Value of a Single CF 5. Example 1: FV example:The NBA's new Larry Bird exception 6. FV Example: NBA's Larry Bird Exception (cont.) 7. SuperStar's Contract Breakdown 8. Present Value of a Single Cash Flow 9. Example 2: Paying Jr, and A-Rod 10. Example 3: Finding Rate of Return or Interest Rate 11. Annuities 12. FV of Annuities 13. PV of Annuities 14. Example 4: Invest Early in an IRA 15. Example 4 Solution 16. Example 5: Lotto Fever 17. Uneven Cash Flows: Example 6:Fun with the CF function 18. Example 6 CF worksheet inputs 19. CF inputs continued 20. Non-Annual Interest Compounding 21. Example 7: What rate are you really paying? 22. Nominal to EAR Calculator 23. Continuous Interest Compounding 24. FV and PV with non-annual interest compounding 25. Non-annual annuities 26. Example 8: Finding Monthly Mortgage Payment 27. solution to Example 8 Graphical rendering by Home Page Reader [HPR]: Example frameset with five links for each of the frame elements in IBM home page reader User agents may also indicate the number of frames in a document and which frame is the current frame via the menu bar or popup menus. Users can configure the user agent to include a FRAMES menu item in their menu bar. The menu bar makes the information highly visible to all users and is very accessible to assistive technologies. In the following image of the Accessible Web Browser [AWB], the menu bar indicates the number of frames and uses a check mark next to the name of the current frame: A pull down menu indicating the number of frames in a document, the labels associated with each frame, and a check mark to indicate the current frame 3.8 Form techniques To make forms accessible, user agents need to ensure that users may interact with them in a device-independent manner, that users can navigate to the various form controls, and that information about the form and its controls is available on demand. 3.8.1 Form navigation techniques * Allow users to navigate to forms and to all controls within a form (refer also to table navigation techniques). Opera [OPERA] and Navigator [NAVIGATOR] provide such functionality in a non-interactive manner, a "form navigation" keyboard commands. When invoked, these "form navigation" commands move the user agent's current focus to the first form control (if any) in the document. * If there are no forms in a document and the user attempts to navigate to a form, alert the user. * Provide a navigable, structured view of form controls (e.g., those grouped by LEGEND or OPTGROUP in HTML) along with their labels. * For labels explicitly associated with form controls (e.g., "for" attribute on LABEL in HTML), make available label information when the user navigates among the form controls. * As the user navigates to a form control, provide information about whether the control must be activated before form submission. * Allow the user to navigate away from a menu without selecting any option (e.g., by pressing the Escape key). * As the user navigates to a form control, provide information (e.g., through context-sensitive help) about how the user can activate the control. Provide information about what is required for each form control. Lynx [LYNX] conveys this information by providing information about the currently selected form control via a status line message: + (Radio Button) Use right-arrow or Return to toggle + (Checkbox Field) Use right-arrow or Return to toggle + (Option List) Press return and use arrow keys and return to select option + (Text Entry Field) Enter Text. Use Up or Down arrows or Tab to move off + (Textarea) Enter text. Up or Down arrows or Tab to move off (^Ve for editor) Note. The ^Ve (caret-V, e) command, included in the TEXTAREA status line message, enables the user to invoke an external editor defined in the local Lynx configuration file (lynx.cfg). 3.8.2 Form orientation techniques Provide the following information about forms on demand: * The number of forms in the document. * The percentage of a form that has already been filled out. This will help users with serial access to form controls know whether they have completed the form. Otherwise, users who encounter a submit button that is not the last control of the form might inadvertently submit the incomplete form. 3.8.3 Form control orientation techniques Provide the following information about the controls in a form on demand (e.g., for the control with focus): * Indicate the number of controls in the form. * Indicate the number of controls that have not yet been completed. * Provide a list of controls that must be activated before form submission. * Provide information about the order of form controls (e.g., as specified by "tabindex" in HTML). This is important since: 1. Most forms are visually oriented, employing changes in font size and color. 2. Users who access forms serially need to know they have supplied all the necessary information before submitting the form. * Provide information about which control has focus (e.g., "control X of Y for the form named "MyForm"). The form name is very important for documents that contain more than one form. This will help users with serial access to form controls know whether they have completed the form. * Allow the user to query a form control for information about title, value, grouping, type, status, and position. * When a group of radio buttons receives content focus, identify the radio button with content focus as "Radio Button X of Y", where "Y" represents the total number of radio buttons in the group. HTML 4.01 specifies the FIELDSET element ([HTML4], section 17.10), which allows authors to group thematically related controls and labels. The LEGEND element ([HTML4], section 17.10) assigns a caption to a FIELDSET. For example, the LEGEND element might identify a FIELDSET of radio buttons as "Connection Rate". Each button could have a LABEL element ([HTML4], section 17.9.1) stating a rate. When it receives content focus, identify the radio button as "Connection Rate: Radio button X of Y: 28.8kpbs", where "Y" represents the total number of radio buttons in the grouping and "28.8kbps" is the information contained in the LABEL. * Allow the user to invoke an external editor instead of editing directly in a TEXTAREA control. This allows users to use all the features of the external editor: macros, spell-checkers, validators, known input configurations, backups and local copies, etc. * Provide an option for transforming menus into checkboxes or radio buttons. In the transformation, retain the accessibility information supplied by the author for the original form controls. Preserve the labels provided for the OPTGROUP and each individual OPTION, and re-associate them with the generated checkboxes. The LABEL defined for the OPTGROUP should be converted into a LEGEND for the result FIELDSET, and each checkbox should retain the LABEL defined for the corresponding OPTION. Lynx [LYNX] does this for HTML SELECT elements that have the "multiple" attribute specified. 3.8.4 Form submission techniques Users (an in particular, users with blindness or any user unaccustomed to online forms) do not want forms to be submitted without their consent. The following techniques address user control of form submissions: * Allow the user to turn off scripts, as authors may write scripts that submit a form when particular events occur (e.g., "onchange" events). Be aware of this type of practice: