[contents] _________________________________________________________________ W3C Techniques for User Agent Accessibility Guidelines 1.0 W3C Working Draft 21-November-1999 This version: http://www.w3.org/WAI/UA/WD-WAI-USERAGENT-TECHS-19991121 (plain text, postscript, pdf, gzip tar file of HTML, zip archive of HTML) Latest version: http://www.w3.org/TR/WAI-USERAGENT-TECHS Previous version: http://www.w3.org/TR/1999/WD-WAI-USERAGENT-TECHS-19991105 Editors: Jon Gunderson, University of Illinois at Urbana-Champaign Ian Jacobs, W3C Copyright © 1999 W3C® (MIT, INRIA, Keio), All Rights Reserved. W3C liability, trademark, document use and software licensing rules apply. _________________________________________________________________ Abstract This document provides techniques for implementing the checkpoints defined in "User Agent Accessibility Guidelines 1.0". These techniques address the accessibility of user interfaces, content rendering, program interfaces, and languages such as HTML, CSS and SMIL. This document is part of a series of accessibility documents published by the Web Accessibility Initiative. 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 Members of 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 to the public mailing list: w3c-wai-ua@w3.org. Mailing list archives are available on the Web. This document has been produced as part of the Web Accessibility Initiative. The goals of the WAI UA Working Group are discussed in the WAI UA charter. A list of the UA 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 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 behavior that may reduce accessibility + 4. Ensure user control over styles + 5. Observe operating system conventions and standard interfaces + 6. Implement open specifications and their accessibility features + 7. Provide navigation mechanisms + 8. Help orient the user + 9. Notify the user of content and viewport changes + 10. Allow the user to configure the user agent + 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 Table techniques + 3.5 Frame techniques + 3.6 Form techniques + 3.7 Script techniques + 3.8 Abbreviations and acronyms * 4 Appendix: Accessibility features of some operating systems * 5 Appendix: Loading assistive technologies for DOM access * 6 Appendix: Assistive Technology Functionalities * 7 Appendix: Terms and Definitions * 8 Acknowledgments * 9 References * 10 Services _________________________________________________________________ 1 Introduction 1.1 Priorities Each checkpoint in this document is assigned a priority that indicates its importance for users. [Priority 1] This checkpoint must be satisfied by user agents as a native feature, otherwise one or more groups of users with disabilities will find it impossible to access information. Satisfying this checkpoint is a basic requirement for some individuals to be able to use the Web. [Priority 2] This checkpoint should be satisfied by user agents as a native feature, otherwise one or more groups of users will find it difficult to access information. Satisfying this checkpoint will remove significant barriers to accessing Web documents. [Priority 3] This checkpoint may be satisfied by user agents as a native feature to make it easier for one or more groups of users to access information. Satisfying this checkpoint will improve access to the Web for some individuals. _________________________________________________________________ 2 User Agent Accessibility Guidelines This section lists each checkpoint of the Guidelines along with some possible techniques for satisfying it. Each checkpoint also links to larger accessibility topics where appropriate. Guideline 1. Support input and output device-independence 1.1 Ensure that every functionality offered through the user interface is available through every input device API used by the user agent. User agents are not required to reimplement low-level functionalities (e.g., for character input or pointer motion) that are inherently bound to a particular API and most naturally accomplished with that API. [Priority 1] Note. The device-independence required by this checkpoint applies to functionalities described by the other checkpoints in this document unless otherwise stated by individual checkpoints. 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: Operating system and application frameworks provide standard mechanisms for controlling application navigation for standard input devices. In the case of Windows, OS/2, the X Windows System, and MacOS, the window manger provides 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. When implementing custom GUI controls do so using the standard input mechanisms defined above. Examples of not using the standard input devices are: + Do not communicate directly with the device. For instance, in Windows, do not open the keyboard device driver directly. This may circumvent system messaging. 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 queue handler. Devices for mobility access, such as those that use serial keys, use standard system facilities for simulating keyboard and mouse input to all graphical applications. Example facilities for generating these input device events are the Journal Playback Hooks in both OS/2 and Windows. These hooks feed the standard system message queues in these respective windowing systems. To the application, the resulting keyboard and mouse input messages are treated as standard input and output device messages generated by the user's actions. + If you implement an interface where the user selects text then issues a command related to it (e.g., select text then create a link using the selected text as content), all operations related to the selection and operation on the selected text must be done in a device-independent manner. In the case of a desktop user agent this means that the user must be able to perform these tasks using either keyboard or mouse. __________________________________________________________ 1.2 Use the standard input and output device APIs of the operating system. [Priority 1] For example, do not directly manipulate the memory associated with information being rendered since screen review utilities, which monitor rendering through the standard APIs, will not work properly. Techniques: + When writing textual information in a GUI operating system, use standard text drawing APIs of an operating system. Text converted to offscreen images or sequences of strokes cannot be intercepted as text drawing calls at the graphics engine or display driver subsystem of a GUI. Legacy screen reading solutions intercept these drawing calls before being transferred to the display and use the text drawn to create a text model representation of what you see on the screen. This "offscreen model" is used to speak GUI text. If you do not use the standard text drawing APIs, legacy screen reading systems will not be able to render it as speech or braille. More information on this is provided in the techniques for checkpoint 1.5. + Use operating system resources for rendering audio information. 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 visual queues when a problem occurs; this benefits users with hearing impairments. These queues may be manifested by flashing the desktop, active caption bar, or active window. It is important to use the standard mechanisms to generated audio feedback so that operating system or special assistive technologies can add additional functionality for the hearing impaired. + 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 mechanisms to give them focus. In this case your will need to add keyboard activation through the standard keyboard activation facility for Abstract Window Toolkit components. + Use standard 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 screen reader from speaking if they use software text-to-speech conversion. __________________________________________________________ 1.3 Ensure that the user can interact with all active elements in a device-independent manner. [Priority 1] For example, users who are blind or have motor impairments must be able to activate the links in a client-side image map without a pointing device. One technique for doing so is to render client-side image maps as text links. Note. This checkpoint is an important special case of checkpoint 1.1. Techniques: Refer to checkpoint 1.1 and checkpoint 1.5. For client-side image maps: + If alternative text ("alt" or "title" in HTML) is available and not null for the element (like INPUT or IMG in HTML) that has an associated client-side map, indicate the presence of a map in text (e.g., "Start of map") plus the alternative text and the number of areas in the map. If alt text is null, do not render the map or its areas. + For each AREA in the map, if alternative text ("alt" or "title") is available and not null, render the alternative text as a link. Otherwise, render some text like "Map area" plus part or all of the href value as a link. If alt "text" is null for an AREA, do not render that AREA. + When reading through the whole Web page, read the start of map alternative text with the number of areas, but skip over the AREA links. To read and activate the map areas, use keys that read and navigate link by link or element by element. Use the document object model to enable device independent activation of elements: + When implementing the DOM ([DOM1], [DOM2]), allow programmatic activation of active elements, whether they are links, links in an image map, or any DOM element that can respond to an event causing a secondary action. + In [DOM2], all elements can be potentially active and it is helpful to allow for activation of all DOM elements by an assistive technology. For example, a DOM2 'focusin' event may result in the construction of a pull-down menu by an attached JavaScript function. Providing a programmatic mechanism of activating the 'focusin' function will allow users to operate the user agent through speech. Each DOM element may have more than one set of activation mechanism based on the DOM event received and it is helpful to enable an assistive technology to enumerate those functions by description and to activate them. An example of this type of functionality can be seen in the Java Accessibility API (refer to [JAVAAPI]). This API provides an an AccessibleAction Java interface. This interface provides a list of actions and descriptions that can be used to describe and activate each function selectively. __________________________________________________________ 1.4 Ensure that every functionality offered through the user interface is available through the standard keyboard API. [Priority 1] The keystroke-only command protocol of the user interface should be efficient enough to support production use. Functionalities include being able to show, hide, resize and move graphical viewports created by the user agent. Note. This checkpoint is an important special case of checkpoint 1.1. Techniques: + Ensure that the user can trigger mouseover, mouseout, click, etc. events from the keyboard consistently. + Ensure that the user can use the keyboard (e.g., to navigate links serially (e.g., through the tab key). + Ensure that the user can use the graphical user interface menus from the keyboard. + Ensure that the keyboard can be used to cut, copy, paste, and drag. + Ensure that the user can select text using the keyboard standards for the platform. + Allow the user to change the state of form controls using the keyboard. + Allow the user to activate events associated with an element using the keyboard, including events that imply device dependence like onMouseOver, MouseClick, etc... __________________________________________________________ 1.5 Ensure that all messages to the user (e.g., informational messages, warnings, errors, etc.) are available through all output device APIs used by the user agent. Do not bypass the standard output APIs when rendering information (e.g., for reasons of speed, efficiency, etc.). [Priority 1] For instance, ensure that information about how much content has been viewed is available through output device APIs. Proportional navigation bars may provide this information graphically, but the information must be available (e.g., as text) to users relying on synthesized speech or braille output. Techniques: 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 MacOS, standard API are provided for writing to the display and the multimedia subsystems. It is important to also support standard output notification of sound such as notifications found in the Windows control panel for sounds. Windows maps accessibility features to the event caused by generation of these specific system sounds. Accessibility features such as SoundSentry will flash the screen, as appropriate, in response to events that would cause these sounds to play. This enables users with hearing i to use the application. When implementing standard output: + Do not render text in the form of bitmap before transferring to the screen. Screen Readers intercept text drawing calls to create a text representation of the screen, called an offscreen model, which is read to the user. 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 provide your own mechanism for generating pre-defined system sounds. + When using a device do not use the device driver directly. In the case of display drivers, screen readers are designed to monitor what is drawn on the screen by hooking drawing calls at different points in the of the drawing process. By calling the display driver directly you may be drawing to the display below the point at which a screen reader for the blind is intercepting the drawing call. + Do not draw directly to the video frame buffer. This circumvents the interception point at which a screen reader hooks the display calls. + Do not forget to provide text alternatives to voiced messages. Make sure an auditory message also has a redundant visual text message. For example, a message like "You've got mail" should also be presented graphically or with text. + Do not preclude text presentation when providing auditory 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 graphically displayed text. __________________________________________________________ Guideline 2. Ensure user access to all content 2.1 Ensure that the user has access to all content, including alternative representations of content. [Priority 1] Note. Although it is not a requirement that alternative content be available at the same time as primary content, some users may benefit from simultaneous access. For instance, users with low vision may want to view images (even imperfectly) but require alternative text for the image to be rendered in a very large size or as speech. Techniques: + 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. + Refer to the section on abbreviations and acronyms. + The "Altifier Tool" (refer to [ALTIFIER]) illustrates smart techniques for generating alternative text for images, etc. when the author hasn't supplied any. + In [HTML40], alternative content may come from the following sources: o For the IMG element: The "alt", "title", and "longdesc" attributes. o For the OBJECT element: The content of the element and the "title" attribute. o For the APPLET element: The "alt" attribute and the content of the element. o For the AREA element: The "alt" attribute. o For the INPUT element: The "alt" attribute. o For the ACRONYM and ABBR elements: The "title" attribute may be used for the acronym or abbreviation expansion. o For the TABLE element, the "summary" attribute. o For frames, the NOFRAMES element and the "longdesc" attribute on FRAME and IFRAME. o For scripts, the NOSCRIPT element. + For information about sources of alternative content in SMIL, refer to [SMIL-ACCESS]. __________________________________________________________ 2.2 If more than one alternative equivalent is available for content, allow the user to choose from among the alternatives. This includes the choice of viewing no alternatives. [Priority 1] For example, if a multimedia presentation has several tracks of closed closed captions (or subtitles) available (e.g., in different languages, different levels of detail, etc.) allow the user to choose from among them. Techniques: + Distinguish image links from their long descriptions ("longdesc" in HTML). + Provide an interface which displays all available tracks, with as much identifying information as the author has provided, and allow users to choose which tracks are rendered. For example, if the author has provided "alt" or "title" for various tracks, use that information to construct the list of tracks. + Provide an interface which allows users to indicate their preferred language separately for each kind of continuous equivalent. The selection can be based on user preferences in either the user agent (cf. the Content-Language entity-header field of [RFC2616], section 14.12) or the operating system. Users with disabilities may need to choose the language they are most familiar with in order to understand a presentation which may not include all equivalent tracks in all desired languages. In addition, international users may prefer to hear the program audio in its original language while reading captions in their first language, fulfilling the function of subtitles or to improve foreign language comprehension. In classrooms, teachers may wish to control the language of various multimedia elements to achieve specific educational goals. The following image illustrates how users select preferred language for captions in the Real Player. Illustration of how user selects preferred language for captions in Real Player The next image illustrates how users select preferred language in the Windows operating system under properties for Regional Settings. This preference could be inherited by the user agent. Illustration of how user selects preferred language in the Windows operating system __________________________________________________________ 2.3 Render content according to natural language identification. [Priority 1] Natural language may be identified by markup (e.g., the "lang" attribute in HTML [HTML40] or "xml:lang" in [XML]) or HTTP headers. Refer also to checkpoint 2.9 and checkpoint 5.3. Techniques: + Use an appropriate glyph set when rendering visually. + Use an appropriate voice set when rendering as speech. + Render characters with the appropriate directionality (refer to "dir" and BDO in [HTML40] and [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, the HTML 4.0 specification (refer to [HTML40], section 5.4) 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. + Refer to [CHARMOD], which defines various aspects of a character model for the World Wide Web. It contains basic definitions and models, specifications to be used by other specifications or directly by implementations, and explanatory material. In particular, early uniform normalization, string identity matching, string indexing, and conventions for URIs are addressed. __________________________________________________________ 2.4 Provide time-independent access to time-dependent active elements or allow the user to control the timing of changes. [Priority 1] Techniques: + Provide access to a static list of time dependent links, including information about the context of the link. 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 viewers to pause the presentation and advance and rewind by small and large time increments. + Allow the user to navigate sequences of related links that vary over time. + Provide a mode in which all active elements are highlighted in some way and can be navigated sequentially. For example, use a status bar to indicate the presence of active elements and allow the user to navigate among them with the keyboard or mouse to identify each element when the presentation is moving and when it is paused. __________________________________________________________ 2.5 Allow the user to specify that continuous equivalent tracks (e.g., closed captions, auditory descriptions, video of sign language, etc.) be rendered at the same time as audio and video tracks. [Priority 1] Techniques: It is important that any continuous equivalent tracks be rendered synchronously with the primary content. This ensures that users with disabilities can use the primary and equivalent content in combination. For example, if a hard-of- hearing user is watching a video and reading captions, it is important for the captions to be synchronized with the audio so that the viewer can use any residual hearing. For audio description, it is crucial that the primary audio track and the audio description track be kept in sync to avoid having them both play at once, which would reduce the clarity of the presentation. User agents that play SMIL ([SMIL]) presentations should take advantage of a variety of access features defined in SMIL (refer to [SMIL-ACCESS]). A future version of SMIL (known currently as SMIL Boston) is in development and additional access features may be available when this specification becomes a W3C Recommendation. As defined in SMIL 1.0, SMIL players should allow users to turn closed captions on and off by implementing the test attribute system-captions which takes the values "on" and "off." For example, include in the player preferences a way for users to indicate that they wish to view captions, when available. SMIL files with captions available should use the following syntax: In this case, when the user has requested captions, this textstream should be rendered, and when they have not it should not be rendered. SMIL 1.0 does not provide a test attribute to control audio description in the same way as captions. Another test attribute, system-overdub-or-captions, allows the user to choose between alternate language text or sound. This attribute specifies whether subtitles or overdub should be rendered for people who are watching a presentation where the audio may be in a language in which they are not fluent. This attribute can have two values: "overdub", which selects for substitution of one voice track for another, and "subtitle", which means that the user prefers the display of subtitles. However, this attribute should not be used to determine if users need closed captions. When both are available, deaf users will prefer to view captions, which contain additional information on music, sound effects, and who is speaking, which are not included in subtitles since those are intended for hearing people. User agents that play QuickTime movies should provide the user with a way to turn on and off the different tracks embedded in the movie. Authors may use these alternate tracks to provide alternative equivalents for use by viewers with disabilities. 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 caption text synchronized with a multimedia presentation. Users should be given a way to indicate their preference for viewing captions. In addition, user agents which play Microsoft Windows Media Object presentations should enable viewers to turn on and off other alternative equivalents, including audio description and alternate video tracks. Other video or animation formats should incorporate similar features. At a minimum, users who are blind and users who are deaf need to be able to turn on and off audio description and and captions. The interface to set these preferences must be accessible. Information on how to author accessible tracks should be included in documentation about the media player. __________________________________________________________ 2.6 If a technology allows for more than one audio track, allow the user to choose from among tracks. [Priority 1] Techniques: + Refer to techniques for [#choose-equivalent]. + Make apparent through the user interface which tracks are meant to be played mutually exclusively. __________________________________________________________ 2.7 When no text equivalent has been specified, indicate what type of object is present. [Priority 2] Techniques: + If no captioning information is available and captioning is turned on, render "no captioning information available" in the captioning region of the viewport. + The "Altifier Tool" (refer to [ALTIFIER]) illustrates smart techniques for generating alternative text for images, etc. when the author hasn't supplied any. + Refer to the section on frame techniques. + Refer to the section on link techniques. __________________________________________________________ 2.8 When alternative text has been specified explicitly as empty (i.e., an empty string), render nothing. [Priority 3] 2.9 For identified but unsupported natural languages, notify the user of language changes when configured to do so. [Priority 3] Techniques: A user agent should treat content language as part of contextual information. When the language changes, the user agent should either render the content in the supported language or notify the user of the language change (if configured for notification). Rendering could involve speaking in the designated language in the case of an audio browser or screen reader. If the language was not supported, the language change notification could be spoken in the default language by a screen reader or audio browser. Language switching for blocks of content may be more helpful than inline language switching. In some language combinations, less than a few words long foreign phrases are often well-integrated in the primary language (e.g., Japanese being the primary and English being the secondary or quoted). In such situations, dynamic switching in in-line level may make the reading sound unnatural, and possibly harder to be understood. Language information for HTML ("lang", "dir") and XML ("xml:lang") should be made available through the DOM ([DOM1]). User agents may announce language changes using style sheets and generating text (refer to [CSS2], [XSLT]) that indicates the change of language. __________________________________________________________ Guideline 3. Allow the user to turn off rendering or behavior that may reduce accessibility In addition to the techniques below, refer also to the section on user control of style. 3.1 Allow the user to turn on and off rendering of background images. [Priority 1] Techniques: + Allow the user to turn off embedded or background images through the user interface. Note that alternative content must still be available for those images. + In [CSS1], background images may be turned on/off with the 'background' and 'background-image' properties. __________________________________________________________ 3.2 Allow the user to turn on and off rendering of background audio. [Priority 1] Techniques: + Allow the user to turn off background audio through the user interface. + Users sometimes specify background sounds with the "bgsound" attribute. Note. This attribute is not part of [HTML40]. + In [CSS2], background sounds may be turned on/off with the 'play-during', property. __________________________________________________________ 3.3 Allow the user to turn on and off rendering of video. [Priority 1] Techniques: + Allow the user to turn off video through the user interface. Render a still image in its place. + Support the 'display' property in CSS. __________________________________________________________ 3.4 When the user agent renders audio natively, allow the user to turn on and off rendering of audio. [Priority 1] Techniques: + Allow the user to turn off audio through the user interface. + Support the 'display', 'play-during', and 'speak' properties in [CSS2]. __________________________________________________________ 3.5 Allow the user to turn on and off animated or blinking text. [Priority 1] Techniques: + Allow the user to turn off animated or blinking text through the user interface (e.g., by hitting 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 CSS 'blink' value of the 'text-decoration' property. __________________________________________________________ 3.6 Allow the user to turn on and off animations and blinking images. [Priority 1] Techniques: + Allow the user to turn off animated or blinking text through the user interface (e.g., by hitting the ESCAPE key to stop animations). Render a still image in its place.x __________________________________________________________ 3.7 Allow the user to turn on and off support for scripts and applets. [Priority 1] 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 in the 4 to 59 flashes per second (Hertz) range. Users should be able, for security reasons, to prevent scripts from executing on their machines. Techniques: Refer to the section on script techniques __________________________________________________________ 3.8 Allow the user to turn on and off rendering of images. [Priority 3] Techniques: Refer to techniques for checkpoint 3.1. __________________________________________________________ 3.9 Allow the user to turn on and off author-specified forwards that occur after a time delay and without user intervention. [Priority 3] Techniques: Content refresh according to an author-specified time interval can be achieved with the following markup in HTML: The user agent should allow the user to disable this type of content refresh. Although no HTML specification defines this behavior formally, some user agents support the use of the META element to refresh the current page after a specified number of seconds, with the option of replacing it by a different URI. Instead of this markup, authors should use server-side redirects (with HTTP). User agents can provide a link to other content rather than changing the content automatically. __________________________________________________________ For example, when forwarding has been turned off, offer a static link to the target. 3.10 Allow the user to turn on and off automatic content refresh. [Priority 3] For example, when turned off, allow the user to refresh content manually instead (through the user interface). Guideline 4. Ensure user control over 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 control font family. [Priority 1] Techniques: + Implement the CSS 'font-family' property. + Allow the user to override the author's specified fonts. + Inherit font information from user's settings for the operating system. __________________________________________________________ 4.2 Allow the user to control the size of text. [Priority 1] For example, allow the user to control font size through style sheets or the user interface. Or allow the user to magnify text. Techniques: + Implement the CSS 'font-size' property. + Allow the user to configure the user agent to ignore author-specified font size. + Inherit font size information from user's settings for the operating system. __________________________________________________________ 4.3 Allow the user to control foreground color. [Priority 1] Techniques: + Implement the CSS 'color' and 'border-color' properties. + Allow the user to specify minimal contrast between foreground and background colors, adjusting colors dynamically to meet those requirements. + Allow the user to impose a specific foreground color, ignoring author-supplied colors. + Inherit foreground color information from user's settings for the operating system. __________________________________________________________ 4.4 Allow the user to control background color. [Priority 1] Techniques: + Implement the CSS 'background-color' property and other background properties. + Allow the user to impose a specific background color, ignoring author-supplied colors. + Inherit background color information from user's settings for the operating system. __________________________________________________________ 4.5 Allow the user to control selection highlighting (e.g., foreground and background color). [Priority 1] Techniques: + For instance, in X Windows, the following resources controls the selection colors in Netscape Navigator: "*selectForeground" and "*selectBackground". + Implement the "HighLightText and "Highlight" predefined color values of [CSS2], section 18.2. + Inherit selection/focus information from user's settings for the operating system. __________________________________________________________ 4.6 Allow the user to control focus highlighting (e.g., foreground and background color). [Priority 1] Checkpoints for applets and animations: 4.7 Allow the user to control animation rate. [Priority 2] Checkpoints for video. 4.8 Allow the user to control video frame rates. [Priority 1] 4.9 Allow the user to control the position of audio closed captions. [Priority 1] 4.10 Allow the user to start, stop, pause, and rewind video. [Priority 2] Checkpoints for audio: 4.11 Allow the user to control audio playback rate. [Priority 1] 4.12 When the user agent renders audio natively, allow the user to control the audio volume. [Priority 2] 4.13 Allow the user to start, stop, pause, and rewind audio. [Priority 2] Checkpoints for synthesized speech: 4.14 Allow the user to control synthesized speech playback rate. [Priority 1] 4.15 Allow the user to control synthesized speech volume. [Priority 1] 4.16 Allow the user to control synthesized speech pitch, gender, and other articulation characteristics. [Priority 2] Checkpoints for the user interface: 4.17 Allow the user to select from available author, user, and user agent default style sheets. [Priority 1] Note. Users should be able to select no style sheets (i.e., turn them off). 4.18 Allow the user to control user agent-initiated spawned viewports. [Priority 2] For example, in HTML, allow the user to control the process of opening a document in a new target frame or a viewport created by author-supplied scripts. In SMIL 1.0, allow the user to control viewports created with show="new". Control may involve prompting the user to confirm or cancel the viewport creation. Users may also want to control the size or position of the viewport and to be able to close the viewport (e.g., with the "back" functionality). Techniques: User agents may: + Allow users to turn off support for spawned viewports entirely + Prompt them before spawning a viewport For example, user agents may recognize the HTML construct target="_blank" and spawn the window according to the user's preference. __________________________________________________________ Guideline 5. Observe operating system conventions and standard interfaces 5.1 Provide accessible APIs to other technologies. [Priority 1] 5.2 Use accessibility resources and conventions of the operating system and supported programming languages, including those for plug-ins and virtual machine environments. [Priority 1] For instance, 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. Techniques: The operating system application programming interfaces (APIs) that support accessibility are designed to provide a bridge between the standard user interface supported by the operating system and alternative user interfaces developed by third-party assistive technology vendors to provide access to persons with disabilities. Applications supporting these APIs are therefore generally more compatible with third-party assistive technology. The User Agent Accessibility Guidelines Working Group strongly recommends using and supporting APIs that improve accessibility and compatibility with third-party assistive technology. Third-party assistive technology can use the accessibility information provided by the APIs to provide an alternative user interface for various disabilities. The following is an informative list of currently public APIs that promote accessibility: + Microsoft Active Accessibility ([MSAA]) in Windows 95/98/NT versions. + Sun Microsystems Java Accessibility API ([JAVAAPI]) in Java Code. Many operating systems have built-in accessibility features for improving the usability of the standard operating system by persons with disabilities. When designing software that runs above an underlying operating system, developers should ensure that the application: 1. Makes use of operating system level features. See the appendix of accessibility features for some common operating systems. 2. Inherits operating system settings related to accessibility. Pertinent settings include font and color information as well as other pieces of information discussed in this document. Write output to and take input from standard system APIs rather than direct from hardware controls where possible. This will enable the I/O to be redirected from or to assistive technology devices - for example, screen readers and braille devices 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. User agents should use standard rather than custom controls when designing user agents. 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. For information about rapid access to Microsoft Internet Explorer's DOM through COM, refer to [BHO]. __________________________________________________________ 5.3 Provide programmatic read and write access to user agent functionalities and user interface controls. [Priority 1] For example, ensure that assistive technologies have access to information about the current input configuration so that they can trigger functionalities through keyboard events, mouse events, etc. Refer also to checkpoint 5.2. 5.4 Implement selection and focus mechanisms and make the selection and focus available to users and through APIs. [Priority 1] Refer also to checkpoint 7.1 and checkpoint 5.3. 5.5 Provide programmatic notification of changes to content and user interface controls (including selection and focus). [Priority 1] Refer also to checkpoint 5.2. 5.6 Conform to W3C Document Object Model specifications and export interfaces defined by those specifications. [Priority 1] For example, refer to [DOM1] and [DOM2]. User agents should export these interfaces using available operating system conventions. Note. The DOM Level 1 specification states that "DOM applications may provide additional interfaces and objects not found in this specification and still be considered DOM compliant." Techniques: A Document Object Model (DOM) is an interface to a standardized tree structure representation of a document. This interface allows authors to access and modify the document with client-side scripting language (e.g., JavaScript) in a consistent manner across scripting languages. As a standard interface, a DOM makes it easier not just for authors but for assistive technology developers to extract information and render it in ways most suited to the needs of particular users. Information of particular importance to accessibility that must be available through the DOM includes: + Content, including alternative content. + Style sheet information (for user control of styles). + Script and event handlers (for device-independent control of behavior). + The document structure (for navigation, creation of alternative views). User agents should implement W3C DOM Recommendations, including [DOM1] and [DOM2]]. The W3C Recommendation for DOM Level 1 ([DOM1]) provides access to HTML and XML document information. The DOM Level 2 ([DOM2]) is made of a set of core interfaces to create and manipulate the structure and contents of a document and a set of optional modules. These modules contain specialized interfaces dedicated to XML, HTML, an abstract view, generic stylesheets, Cascading Style Sheets, Events, traversing the document structure, and a Range object. It is important to note that DOM is designed to be used on a server as well as a client and therefore many user interface-specific information such as screen coordinate information is not relevant and not addressed by the DOM specification. Assistive technologies also require information about browser highlight mechanisms (e.g., the selection and focus) that may not be available through the W3C DOM. Note. The WAI Protocols and Formats Working Group is focusing its efforts on the DOM as the conduit from which to extract accessibility information from and to enhance the accessibility of a rendered document through a user agent. It is this are should concentrate on for providing access to user agent documents. __________________________________________________________ 5.7 Provide programmatic exchange of information in a timely manner. [Priority 2] This is important for synchronous alternative renderings and simulation of events. 5.8 Follow operating system conventions and accessibility settings. In particular, follow conventions for user interface design, default keyboard configuration, product installation, and documentation. [Priority 2] Refer also to checkpoint 10.5. Techniques: Develop the UA User Interface (UI) with standard interface components per the target platform(s). Most major operating system platforms provide a series of design and usability guidelines, these should be followed when possible (see platforms below). These checklists, style guides, and human interface guidelines provide very valuable information for developing applications (e.g., UAs) for any platform/operating system/GUI. If your custom interface cannot provide information or operation as defined above, then you may need to design your UA using any additional options provided by that platform. For instance, software should use the standard interface for keyboard events rather than working around it. Evaluate your standard interface components on the target platform against any built in operating system accessibility functions (see Appendix 8) and be sure your UA operates properly with all these functions. For example, take caution with the following: + 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. + Apple Macintosh supports an accessibility function called "Sticky Keys". Sticky Keys operates with keys the operating system understands to be defined as modifier keys, and therefore a custom UA control should not attempt to define a new modifier key. Some guidelines for specific platforms: + "Macintosh Human Interface Guidelines" [APPLE-HI] Apple Computer Inc. + "IBM Guidelines for Writing Accessible Applications Using 100% Pure Java" [JAVA-ACCESS]. + "An ICE Rendezvous Mechanism for X Window System Clients" [ICE-RAP]. + "Information for Developers About Microsoft Active Accessibility" [MSAA]. + "The Inter-Client communication conventions manual" [ICCCM]. + "Lotus Notes accessibility guidelines" [NOTES-ACCESS]. + "Java accessibility guidelines and checklist" [JAVA-CHECKLIST]. + "The Java Tutorial. Trail: Creating a GUI with JFC/Swing" [JAVA-TUT]. + "The Microsoft Windows Guidelines for Accessible Software Design" [MS-SOFTWARE]. General guidelines for producing accessible software: + "Accessibility for applications designers" [MS-ENABLE]. + "Application Software Design Guidelines" [TRACE-REF]. + "Designing for Accessibility" [SUN-DESIGN]. + "EITAAC Desktop Software standards" [EITAAC]. + "Requirements for Accessible Software Design" [ED-DEPT]. + "Software Accessibility" [IBM-ACCESS]. + Towards Accessible Human-Computer Interaction" [SUN-HCI]. + "What is Accessible Software" [WHAT-IS]. + Accessibility guidelines for Unix and X Window applications [XGUIDELINES]. Follow System Conventions for loading Assistive Technologies: User agents should follow operating system or application environment (e.g., Java) conventions for loading assistive technologies. In the case of Java applets, the browser's Java Virtual Machine should follow the Sun convention for loading an assistive technology. Writing an application that follows the Java system conventions for accessible software does not allow the applet to be accessible if an assistive technology designed for that environment cannot be run to make the applet accessible. 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. __________________________________________________________ Guideline 6. Implement open specifications and their accessibility features 6.1 Implement the accessibility features of supported specifications (markup languages, style sheet languages, metadata languages, graphics formats, etc.). [Priority 1] Note. The Techniques Document ([UA-TECHNIQUES]) discusses accessibility features of W3C specifications. Techniques: + The accessibility features of Cascading Style Sheets (refer to [CSS1] and [CSS2]) are described in [CSS-ACCESS]. + The accessibility features of SMIL 1.0 (refer to [SMIL]) are described in [SMIL-ACCESS]. + The following is a list of accessibility features of [HTML40]: o The "alt" attribute defined for the IMG, AREA, INPUT, and APPLET elements. o The "longdesc" attribute defined for IMG elements ([HTML40], section 13.2). This attribute may be used to attach additional descriptive information to images if the "alt" description is insufficient. o The CAPTION element ([HTML40], section 11.2.2) for rich table captions. o The ACRONYM and ABBR elements ([HTML40], section 9.2.1) for acronyms and abbreviations. o The "summary" attribute for TABLE ([HTML40], section 11.2.1) for table summary information. o Table elements (THEAD, TBODY, TFOOT, COLGROUP, and COL) that group table rows and columns into meaningful sections. o Attributes ("scope", "headers", and "axes") so that non-visual browsers may render a table in a linear fashion, based on the semantically significant labels. o The NOSCRIPT element ([HTML40], sections 18.3.1 and 16.4.1) for accessible alternatives to scripts. o The NOFRAMES element ([HTML40], sections 18.3.1 and 16.4.1) for accessible alternatives to frames. o Support the "lang" attribute ([HTML40], section 8.1). o The "tabindex" attribute ([HTML40], section 17.11.1) for assigning the order of keyboard navigation within a document. o The "accesskey" attribute ([HTML40], section 17.11.2) for assigning keyboard commands to active components such as links, and form controls. __________________________________________________________ 6.2 Conform to W3C specifications when they are appropriate for a task. [Priority 2] For instance, for markup, implement [HTML40] or [XML]. For style sheets, implement [CSS1], [CSS2], or [XSLT]. For mathematics, implement [MATHML]. For synchronized multimedia, implement [SMIL]. For access to the structure of HTML or XML documents, implement [DOM1]. For an event model, implement [DOM2]. Refer also to checkpoint 5.6. Guideline 7. Provide navigation mechanisms 7.1 Allow the user to navigate viewports (including frames). [Priority 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 displayed individually (e.g., by a text browser or speech synthesizer), provide a list of links to individual frames. Navigating into a viewport makes it the current viewport. Techniques: + Some operating systems provide a means to navigate among all windows, not just those created by the user agent. This suffices for viewports that are windows. However user agents may also allow the user to shift the focus from window to window independent of the standard operating system mechanism. + Consult the section on frame techniques. __________________________________________________________ 7.2 For user agents that offer a browsing history mechanism, when the user returns to a previous view, restore the point of regard in the viewport. [Priority 1] For example, when users navigate "back" and "forth" among views, for each view they should find the viewport position where they left it. 7.3 Allow the user to navigate just among cells of a table (notably left and right within a row and up and down within a column). [Priority 1] Note. Navigation techniques include keyboard navigation from cell to cell (e.g., using the arrow keys) and page up/down scrolling. Refer also to checkpoint 1.1 and checkpoint 5.3. Techniques: All users should be able to quickly determine the nature and purpose of a table. Examining the table visually often conveys a sense of the table contents with a quick scan of the cells. Users with blindness or low vision, users who have difficulty translating printed material, or users in an eyes-busy or speech-based environment may not able to do this. Providing table summary information, when first navigating to a table allows the nature of a table to be easily determined. In HTML, summary information for tables comes from the "summary" attribute on the TABLE element as well as the CAPTION element. An auditory rendering agent, when the point-of-regard moves to a table, might say, "Table: Tax tables for 1998," thus identifying the nature of the table. The user could then use keyboard commands to move the selection to the next logical block of information, or use a different command to "burrow" into the table. The "burrow" command should have an opposite "up" command, which would move the selection from an individual cell to the table as a whole, so that the user can leave a table from any cell within it, rather than navigating to the end. If the user moves the focus up to look over the summary information, it should be possible to burrow back to the same cell. When navigating a table that contains another table, this strategy can avoid confusion. For example, if each row of a table contained five cells, but the second row contained a 4x4 table in the third cell, a user could be disoriented when the row did not end as expected. However, when the selection moved to the third cell of the table, a compliant browser would report that this was a table, and describe its contents. The user would have the option of navigating to the forth cell of the parent table, or burrowing into the table within this cell. When rendering tabular information, the fact that it is tabular information should be apparent. For a graphical user agent, such information is commonly made obvious by the border attribute or by visually apparent aligned white space between columns. However, for a non-graphical agent, such information must also be made evident. As the user agent shifts the selection to a table, it should first allow users to access summary information about the table (e.g., the CAPTION element or the "summary" attribute in HTML). Access to this information allows the user to determine whether or not to examine the contents of the table, or to move the selection to the next block of content. Users should be able to choose not to have the summary information presented, if, for example, they visit a table frequently and don't want to hear the summary information repeated each time. In many data tables, the meaning of the contents of a cell are related to the contents of adjacent cells. For example, in a table of sales figures, the sales for the current quarter might be best understood in relation to the sales for the previous quarter, located in the adjacent cell. In order to provide access to contextual information for individuals using non-graphical browsers, or for individuals with certain types of learning disabilities, it is necessary for the user agent to allow the selection to be moved from cell to cell, both right/left and up/down via keyboard commands. The UA should inform the user when navigation has led to a table edge. The most direct method of performing such navigation would be via the cursor keys, though other navigation strategies might be used. Users of graphical browsers can easily locate cells within a table that are at the intersection of a row and column of interest. To provide equivalent access to users of non-graphical browsers, equivalent means of navigation should be provided. The search function of a browser will allow the user to locate key terms within a table, but will not allow the user to find cells that are at the intersection of rows and columns of interest. More techniques: + An advanced search mode might provide entries for header information, allowing the user to find information at the intersection of columns and rows using the key terms. + A search mode might allow the user to search for key terms that are related to key header terms, allowing searches to be restricted to specific rows or headers within a table. The header information visible in a TH cell may be abbreviated, in which case it should be user preference to see the "abbr" value if any or the full contents. Axis information may also help the user search into confined portions of the table. Column groups and row groups are other confining partitions of a table in which a search may be limited. Software: + Table navigation script from the Trace Center __________________________________________________________ 7.4 Allow the user to navigate all active elements. [Priority 1] Navigation mechanisms may range from sequential (e.g., serial navigation by tabbing) to direct (e.g., by entering link text) to searching on active elements only (e.g., based on form control text, associated labels, or form control names). 7.5 Allow the user to navigate just among all active elements. [Priority 2] Refer also to checkpoint 7.4. Techniques: Sequential navigation includes all active elements. User agents might provide other navigation mechanisms limited to a particular type of element. For example "Find the next table" or "Find the previous form". The following techniques suggest some types of navigation. + Serial navigation. It is important that application developers maintain a logical keyboard navigation order. The navigation order is defined as the order of navigation among components and component elements via the keyboard. Generally users navigate by tabbing between components or groups and using the arrow keys within a component group or component's elements. The ability to tab between software components is a key feature in the implementation of keyboard accessibility. (Cross-reference to keyboard access.) Buttons of common functionality, such as a set of radio buttons used to set the location of a panel (top left, bottom left, and so on.), should be grouped together so the first element of the visible group can be tabbed to. Allow the user to use the arrow keys to navigate to each end of the group. + How to indicate that something is in tabbing order in Java: A component is inclusive in the tabbing order when added to a panel and its isFocusTraversable() method returns true. A component can be removed from the tabbing order by simply extending the component, overloading this method, and returning false. + For active elements, navigation to the previous or next active element. + In a table, up/down and left/right. Direct navigation: Excessive use of serial navigation can reduce the usability of software for both disabled and non-disabled users. As a developer, you need to determine the point at which tabbing gets in the way and provide a keyboard alternative. This is done through the use of keyboard shortcuts. Note that user agents must provide information about available shortcuts (the current keyboard configuration) to users. + Need for element identification. + Access by position in document. + Next/Previous occurrence of text in an element's content (e.g., first letter) in the current document. + In a table, access to cell based on coordinates. __________________________________________________________ 7.6 Allow the user to search for rendered text content, including alternative text content. [Priority 2] Techniques: + Allow users to search for element content and attribute values (human-readable ones). + Allow users to search the document source view. + For forms, allow users to find required controls. Allow users to search on labels as well as content of some controls. + Allow the user to search among just alternative text. + 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 search closest timestamp from a text stream or a media elements or links and find other media elements active at the same time. 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). __________________________________________________________ 7.7 Allow the user to navigate according to structure. [Priority 2] For example, allow the user to navigate familiar elements of a document: paragraphs, tables, headers, lists, etc. Techniques: + DOM is minimal (tree navigation) + Best navigation will involve a mix of source tree information and rendered information. + May use commonly understood document models rather than strict DTD navigation. E.g., properly nesting headers in HTML. Headers should be used only to convey hierarchy, not for graphical side-effects. + Goal of simplifying the structure view as much as possible. + Allow the user to control level of detail/ view of structure. + Depth first as well as breadth first possible. Allow next/previous sibling, up to parent, and end of element. + Navigation of synchronized multimedia: allow users to stop, pause, fast forward, advance to the next clip, etc. + In a speech-based user interface, allow the user to navigate letters, words, sentences and other language-dependent pieces of text content. Skipping navigation bars: Author-supplied navigation mechanisms such as navigation bars at the top of each page may force users with screen readers or some physical disabilities to wade through numerous links on each page of a site. 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 doing so include: 1. Provide 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 4.0, the MAP element allows block content, not just AREA elements. __________________________________________________________ 7.8 Allow the user to configure structured navigation. [Priority 3] 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 expand or shrink portions of the structured view (control detail level) for faster access to important parts content. __________________________________________________________ Guideline 8. Help orient the user 8.1 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current viewport, selection, and focus. [Priority 1] Note. This includes highlighting and identifying frames. Refer also to checkpoint 9.1.. Techniques: + If colors are used to highlight the current viewport, selection, or focus, allow the user to set preferred colors and to ensure sufficient contrasts. + If the current viewport is a window, allow the user to cause the window to pop to the foreground. + If the current viewport is a frame or the user doesn't want windows to pop to the foreground, use colors, reverse videos, or other visual clues to indicate the current viewport. For speech or braille output, render the title or name of a frame or window and indicate changes in the current viewport. + Use operating system conventions, where available, for specifying selection and focus (e.g., schemes in Windows). + Implement the CSS pseudo-classes ':hover', ':active', and ':focus'. This will allow users to modify focus presentation in user style sheets. Refer also to the section on frame techniques The following image illustrates the use by Opera 3.6 of a solid line border to indicate focus: Example of a solid line border used to indicate the focus in Opera 3.60 The following image illustrates the use of system highlight colors to indicate focus: Example of system highlight colors used to indicate the focus by the accessible browser project The following image illustrates the use of a dotted line border to indicate focus: Example of dotted line border used to indicate the focus in Internet Explorer 5.0 and Netscape Navigator 4.7 __________________________________________________________ 8.2 Convey the author-specified purpose of each table and the relationships among the table cells and headers. [Priority 1] For example, provide information about table headers, how headers relate to cells, table caption and summary information, cell position information, table dimensions, etc. Note. This checkpoint is an important special case of checkpoint 2.1. Techniques: + Refer to the section on table techniques + Allow the user to access this information on demand (e.g., by activating a menu or keystroke). __________________________________________________________ 8.3 Provide an outline of a resource view built from its structural elements (e.g., frames, headers, lists, forms, tables, etc.) [Priority 2] 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. 8.4 Indicate whether a focused link has been marked up to indicate that following it will involve a fee. [Priority 2] Note. [MICROPAYMENT] describes how authors may mark up micropayment information in an interoperable manner. This information may be provided through the standard user interface provided the interface is accessible. Thus, any prompt asking the user to confirm payment must be accessible. Techniques: + Refer to the section on link techniques. + Allow the user to access this information on demand (e.g., by activating a menu or keystroke for a focused link). __________________________________________________________ 8.5 Provide information to help the user decide whether to follow a focused link. [Priority 2] Note. Useful information includes: whether the link has already been visited, whether it designates an internal anchor, the type of the target resource, the length of an audio or video clip that will be started, and the expected natural language of target resource. Techniques: + Refer to the section on link techniques. + Allow the user to access this information on demand (e.g., by activating a menu or keystroke). + Implement CSS ':visited' and ':link' pseudo-classes, with ':before' class and the 'content' property to insert text before a link such as "visited" or "un-visited". __________________________________________________________ 8.6 Allow the user to configure the outline view. [Priority 3] For example, allow the user to control the level of detail of the outline. Refer also to checkpoint 8.3. Refer also to checkpoint 5.3. 8.7 Allow the user to configure what information about links to present. [Priority 3] Note. Using color as the only distinguishing factor between visited and unvisited links does not suffice since color may not be perceivable by all users or rendered by all devices. Refer also to checkpoint 8.5. Techniques: + Allow the user to access this information on demand (e.g., by activating a menu or keystroke). + Implement CSS ':visited' and ':link' pseudo-classes, with ':before' class and the 'content' property to insert text before a link such as "visited" or "un-visited". __________________________________________________________ 8.8 Provide a mechanism for highlighting and identifying (through a standard interface where available) active elements. [Priority 3] Note. User agents may satisfy this checkpoint by implementing the appropriate style sheet mechanisms, such as link highlighting. 8.9 Maintain consistent user agent behavior and default configurations between software releases. Consistency is less important than accessibility and adoption of operating system conventions. [Priority 3] In particular, make changes conservatively to the layout of user interface controls, behavior of existing functionalities, and default keyboard configuration. Guideline 9. Notify the user of content and viewport changes 9.1 Provide information about user agent-initiated content and viewport changes directly to the user and through APIs. [Priority 1] For example, inform the users when a script causes a popup menu to appear. Techniques: + Refer to the section on frame techniques + Render the changed content graphically. + Highlight the current viewport. + Emit an audible signal when a change occurs. + Make DOM methods fire a "change" event that can be trapped (does [DOM2] have this already?) __________________________________________________________ 9.2 Ensure that when the selection or focus changes, it is in the viewport after the change. [Priority 2] Techniques: + There are time when the 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 focus must be moved to follow it. In both cases, the focus (or selection) is in the viewport after the change. + Make sure that search windows do not place the new focus that is the found object under a search popup. + Only change selection/focus in the current viewport. __________________________________________________________ 9.3 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] Techniques: + Put up a dialog indicating the form will be submitted if it is done by an onChange, after a certain time, or for other script-based submission. Allow the user to suppress these dialogs for good. + If the submit button is not the last control in the form, and no controls after it have been focussed, put up a dialog pointing this out/asking if the user has filled in the information after the button. + If a Javascript submission is fired, allow the user to ask for it to be intercepted and trigger the dialog mentioned above. __________________________________________________________ For example, do not submit a form automatically when a menu option is selected, when all fields of a form have been filled out, on a mouseover event, etc. 9.4 Allow the user to configure notification preferences for common types of content and viewport changes. [Priority 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, img, ...) + Allow the user to disable notification of changes to CSS properties + Allow the user to disable notification of images that are changed __________________________________________________________ 9.5 When loading content (e.g., document, video clip, audio clip, etc.) indicate what portion of the content has loaded and whether loading has stalled. [Priority 3] Techniques: Status information - on resource loading - should be provided in a device-independent manner. Techniques include text and non-text status indicators. Users should be able to request status information or have it rendered automatically. User agents may allow users to configure when status information should be rendered (e.g., by hiding or showing the status bar). Screen readers may provide access on demand (e.g., through the keyboard) to the most recent status information, or to announce the new information whenever it changes. Useful status information: + Document proportions (numbers of lines, pages, width, etc.) + Number of elements of a particular type (e.g., tables) + The viewport is at the beginning or end of the document. + Size of document in bytes. User agents may allow users to configure what status information they want rendered. Allow users to access status information on demand through a keyboard or other shortcut. __________________________________________________________ 9.6 Indicate the relative position of the viewport in 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] Note. Depending on how the user has been browsing, the percentage may be calculated according to focus position, selection position, or viewport position. Techniques: + Provide a scrollbar for the viewport. + List the current "page" as page X of a total of Y pages. + Use a variable pitch audible signal to indicate position. + Keep the information numerically and generate the output on user request. See new HTML work on Forms for further examples (a slider is like a dial is like a menu of lots of options...) + Provide standard markers for specific percentages through the document (mile posts) + 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 the user to configure the user agent 10.1 Provide information about the current user-specified input configuration (e.g., keyboard or voice bindings specified through the user agent's user interface). [Priority 1] Techniques: If the current configuration changes locally (e.g., a search prompt opens that changes the keyboard mapping for the duration of the prompt), the user must be able to know about the current configuration. Users may have an easier time remembering named configurations - "this is the configuration in this particular mode." Information about tabbing order: + Specified by "tabindex" in [HTML40]. + Provide a list of form controls according to the tabbing order of the form. This allows users to know whether, for example, a submit button is the last control in a form or whether the user must activate controls that follow it. + Provide a structured view of form controls (e.g., those grouped by LEGEND or OPTGROUP in HTML) along with their labels. Information about keyboard shortcuts: + Specified by "accesskey" in [HTML40]. + Use system conventions to indicate the current configuration. + Document the default configuration. + Allow direct access to active elements (links, form controls, etc.). For instance, through a menu that allows users to enter a link number of link text and to move the focus there. + Allow the user to separate setting the focus and activating the control. For links, first-time users of a page may want to hear link text (focus) before deciding whether to follow the link (activate). More experienced users of a page would prefer to follow the link directly, without the intervening focus step. Distinguish the following classes of input configurations: + The defaults "out of the box". + The current defaults if different from those out of the box. + Those in effect for the current document only. + Those that have been overridden by the configuration of the current document. Also, how to access functionalities no longer available due to the current input configuration. Some reserved keyboard shortcuts are listed in the appendix on accessibility features of some operating systems. In case of conflicts between author-supplied configuration and user-supplied, operating system defaults, or user agent default configurations, here is some possible behavior: + Do not override default system and user agent controls, but alert the user of author-supplied configuration and provide a pass-through mechanism to allow author-specified configurations that conflict with default UA or OS keybindings to be invoked. + Allow author-defined configurations to override user agent and operating system configurations, but alert the user of the conflicts and provide a pass-through mechanism so that the conflicting user agent or operating system configurations can be invoked. + Remap author-supplied configurations to currently unused keystrokes, voice commands, etc. and alert the user to which configurations have been remapped. __________________________________________________________ 10.2 Provide information about the current author-specified input configuration (e.g., keyboard bindings specified in content such as by "accesskey" in [HTML40]). [Priority 2] Techniques: Distinguish the following classes of user input bindings: + bindings that are in effect and agree with the shipping defaults for the base browser + bindings that are in effect but differ from the shipping defaults + bindings that are in effect for this document only (subset of previous class) + bindings no longer in effect because they have been overridden In association with local (e.g., this page only) and off-default bindings, provide information about how to work around the override. Note that user support personnel, particularly remote support personnel, will need the "departures from shipping defaults" view for orientation. The above classes may be distinguished by displayed properties in a combined presentation as well as by filtering to present only a restricted class. __________________________________________________________ 10.3 Allow the user to change and control the input configuration. Users should be able to activate a functionality with a single-stroke (e.g., single-key, single voice command, etc.). [Priority 2] Users should not be required to activate functionalities by navigating through the graphical user interface (e.g., by moving a mouse to activate a button or by pressing the "down arrow" key repeatedly in order to reach the desired activation mechanism. Input configurations should allow quick and direct access that does not rely on graphical output. For self-voicing browsers, allow the user to modify what voice commands activate functionalities. Similarly, allow the user to modify the graphical user interface for quick access to commonly used functionalities (e.g., through buttons). Techniques: User agents that allow users to customize or reconfigure mappings from keyboard, voice, etc. to user agent functionalities should allow each mapping to be accompanied by a description so that the user can understand the mapping. For example, if "Control-P" maps to a print functionality, a short description would be "Print" or "Print setup". + Profiles + Default values + Device-independent configuration When using a physical keyboard, some users require single-key access, others require that keys activated in combination be physically close together, while others require that they be spaced physically far apart. When allowing users to configure keyboard access to functionalities, user agents must consider operating system conventions, author-specified shortcuts, and user preferences. The user agent's default configuration should include shortcuts for frequently performed actions and should respect operating system conventions. User agents, to allow the user to turn on and off author-specified keyboard configurations, may offer a checkbox in the keyboard mapping dialog to that would toggle the support for author-specified keyboard configurations. In [HTML40], authors may specify keyboard behavior with the "tabindex" and "accesskey" attributes. __________________________________________________________ 10.4 Use operating system conventions to indicate the input configuration. [Priority 2] 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. Techniques: In some operating systems, information about shortcuts is rendered visually using an underscore under a character in a menu item or button corresponding to the shortcut key activated with an ALT+character. For menu accelerators the text in the menu item is often followed by a CNTRL+function key. These are conventions used by the Sun Java Foundations Classes (refer to [JAVA-TUT]) and Microsoft Foundations Classes for Windows. __________________________________________________________ 10.5 Avoid default input configurations that interfere with operating system conventions. [Priority 2] For example, the default configuration should not include "Alt-F4" or "Control-Alt-Delete" on operating systems where that combination has special meaning to the operating system. In particular, default configurations should not interfere with the mobility access keyboard modifiers reserved for the operating system. Refer also to guideline 5. 10.6 Allow the user to configure the user agent in named profiles that may be shared (by other users or software). [Priority 2] Users must be able to select from among available profiles or no profile (i.e., the user agent default settings). Techniques: Configuration profiles allow individual users to save their user agent settings and re-apply them easily. This is particularly valuable in an environment where several people may use the same machine. Profiles may include rendering preferences as well as user email address, proxy information, stylesheet preferences, etc. The user should be able to easily transfer profiles between installations of the same user agent. One way to facilitate this is to follow applicable operating system conventions for profiles. Users should be able to switch rapidly between profiles (or the default settings) and to set a new default profile. This is helpful when: + Several people use the same machine. + One user is being helped by another who may not recognize the information being displayed using the user's profile. User agents may apply a profile when the user logs in. They may also allow users to apply settings interactively, for example by allowing them to choose from a list of named profiles in a menu. Sample profiles (based on common usage scenarios) can assist users in the initial set up of the user agent. These profiles can serve as models and may be copied and fine-tuned to meet an individual's particular needs. Cascading Style Sheets may be part of a source document or linked externally. Stand-alone style sheets are useful for implementing user profiles in public access computer environments where several people use the same computer. User profiles allow for convenient customization and may be shared by a group. __________________________________________________________ 10.7 Provide default input configurations for frequently performed operations. [Priority 3] Make it easy to use the most frequently requested commands. In particular, provide convenient mappings to functionalities that promote accessibility such as navigation of links. 10.8 Allow the user to configure the graphical arrangement of user interface controls. [Priority 3] 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 change the position of control bars, icons, etc. Do not rely solely on drag-and-drop for reordering tool bar; the user must be able to configure the user interface in a device-independent manner (e.g., through a text-based profile). __________________________________________________________ Guideline 11. Provide accessible product documentation and help 11.1 Provide a version of the product documentation that conforms to the Web Content Accessibility Guidelines. [Priority 1] User agents may provide documentation in many formats, but one must be accessible as per [WAI-WEBCONTENT]. Alternative content, navigation mechanisms, and illustrations will all help make the documentation accessible. Techniques: It is essential that any 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, conform to [WAI-WEBCONTENT]. This includes (but is not limited to): 1. alternative textual descriptions of all graphics 2. extended descriptions of screen-shots, flow-charts, etc. 3. clear and consistent navigational mechanisms 4. use of the NOFRAMES element when the support/documentation is presented in a FRAMESET 5. serial listings of keystrokes and keybindings Accessing documentation in familiar applications is particularly important to users with disabilities who must learn the functionalities of their tools and be able to configure them for their needs. Commonly used applications are also more likely to be compatible with assistive technology. Electronic documentation should not be provided in proprietary formats. Run-time help and any Web-based help or support information, as well as the documentation distributed with the tool, must be fully accessible to persons with disabilities. As per checkpoint 1.1, the user must be able to invoke the run-time help with a simple, well documented keystroke command. It is strongly suggested that the keybinding used to invoke the UAs help system be the default "Help" keybinding for the operating system. Users with print impairments may need or desire documentation in alternative formats such as Braille (refer to [BRAILLEFORMATS]), large print, or audio tape. User agent manufacturers may provide user manuals in alternative formats. Documents in alternative formats can be created by agencies such as Recording for the Blind and Dyslexic and the National Braille Press. User instructions should be expressed in an input device-independent manner. Provide instructions for using or configuring the user agent in a manner that can be understood by a user of any input device including a mouse or keyboard. For example, "Select the Home button on the toolbar" or "Select Home from the Go menu to return to the Home page." Universal design means that access to features that help accessibility should be integrated into standard menus. User agents should avoid regrouping access to accessibility features into specialized menus. Proper documentation is important to developers with disabilities, not just users with disabilities. A disabled user may be a developer using the user agent as a test bed or someone who needs critical information that can only be obtained by as direct a path to the tool's mechanics and "under-the-hood" features as possible. Detailed accessible documentation (e.g., distributed on CD-ROM) is important to allow assistive technology developers access to APIs, etc. __________________________________________________________ 11.2 Document all user agent features that promote accessibility. [Priority 1] For example, review the documentation or help system to ensure that it discusses the functionalities addressed by the checkpoints of this document. Techniques: Include references to accessibility features in these parts of the documentation: 1. Indexes. Include terms related to product accessibility in the documentation index (e.g., "accessibility", "disability" or "disabilities"). 2. Tables of Contents. Include terms related to product accessibility in the documentation table of contents (e.g., features that promote accessibility) 3. Include instructions on how to modify all user configurable defaults and preferences (e.g, images, video, style sheets, and scripts) as specified by the documentation. 4. Include a list of all keyboard shortcuts or other input configuration information in the accessibility section of the documentation. 5. Document the features implemented to conform with these Guidelines. __________________________________________________________ 11.3 Document the default input configuration (e.g., default keyboard bindings). [Priority 1] For example, documentation of what user agent features may be activated with a single keystroke, voice command, or button activation is an important part of the user interface to users with visual impairments, some types of movement impairments, or multiple disabilities. Without this documentation,these users may not realize they can accomplish a particular task with a single gesture and so might unnecessarily avoid that feature of the software. Or they might waste time and energy using a very inefficient technique to perform a task. Techniques: Here is a table showing mappings between Netscape Navigator functions (or potential functions) and their keyboard shortcuts in Macintosh, Unix, and Windows versions. 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. A serialized version of this information should be available in addition to this table. Some entries contain links to special notes. The number in parentheses following the link is the number of the relevant note. CAPTION: Netscape 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 * * Ctrl-Home Scroll to bottom * * Ctrl-End Move between documents Open a new document Command+L Alt+O Ctrl+O Stop loading a document Command+. Esc Esc Refresh a document Command+R Alt+R Ctrl+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 Ctrl+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 Ctrl+D Edit bookmarks Command+B Alt+B Ctrl+B Delete current bookmark (5) Delete Alt+D Delete Navigate history list View history list Command+H Alt+H Ctrl+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 Ctrl+W Define view Increase font size (7) Shift+Command+] Alt+] Ctrl+] Decrease font size (7) Shift+Command+[ Alt+[ Ctrl+[ 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 ? ? ? Notes. 1. In Windows, active elements can be 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 focus using keyboard commands. In Unix and Macintosh, this only applies to the "Submit" button following a text entry. 3. In Unix, the menus can not 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 can not 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 (css). Although Netscape 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 cascading style sheets 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, document all features of the user agent that promote accessibility. [Priority 2] Techniques: When providing, in a dedicated section, documentation for all features of the user agent that promote accessibility, it is also essential that such information be clearly and obviously linked to other sections of the documentation, where appropriate. A dedicated section documenting the features of the user agent that promote accessibility, however, must not be the only method of documenting such features. __________________________________________________________ _________________________________________________________________ 3 Accessibility Topics This section introduces some general techniques to promote accessibility in user agent functionality. A list of assistive technologies and browsers designed for accessibility is available at the WAI Web site (refer to [USERAGENTS]). 3.1 Access to content Users must have access to document content, however they are browsing. Content can come from: * the document source, both primary and alternative content. Document source includes element content, attribute values, and referenced content (e.g., images). * style sheets. * the user agent. The most basic way to give users access to content is to render the entire document in one stream, whether it be a two-dimensional graphical layout, audio stream, or line-by-line braille stream). However, user agents should do much more to ensure that users can understand a page by: * Preserving structure when rendering * Allowing the user to select specific content and query its structure or context * Allowing access to alternative content. * Using and generating metadata to provide context * Allowing the user to configure the user agent for different rendering options These topics are addressed below. 3.1.1 Preserve and provide structure Retain structure when rendering. For example, a graphical rendering of tables conveys relationships among cells. Serial renderings (e.g., to speech) must also make those relationships apparent, otherwise users will not know where a table cell ends, or a list item, etc. One technique for maintaining structure is to precede content with "header" information (upon user demand). For example, give the position of a table cell or it's associated headers. Or indicate the position of a list item within nested lists. Provide "intelligent" structure that may not be exactly what the DTD says. For instance, in HTML, header elements do not nest, but presenting the document as hierarchical may give users a better sense of document structure. Use common idioms where known, even if they are not expressly in the DTD. 3.1.2 Allow access to selected content In the Amaya browser ([AMAYA]), users may access attribute values as follows: Place the cursor at the element in question, open/swap to the structure view. You are shown list of attributes and values. Another technique: select the element (press escape in Linux), then the attributes are all available from the attributes menu. For alt, one can also look at the alternate view, which renders alt text instead of images - a lynx-like view. All the views are synchronized for navigation (and for editing). Users may want to select content based on the rendering structure alone (i.e., that amounts to selecting across element borders). Users may want to select content based on structure (e.g., a table cell). Amaya allows users to "climb" the document tree by positioning the cursor and pressing the Escape key. Each Escape selects one node higher in the document tree, up to the root. 3.1.3 Access to alternative content Speech-based user agents providing accessible solutions for images should, by default, provide no information about images for which the author has provided no alternative text. The reason for this is that the image will clutter the user's view with unusable information adding to the confusion. In the case of an speech rendering, nothing should be spoken for the image element. This user should be able to turn off this option to find out what images were inaccessible so that the content author could be contacted to correct the problem. In the case of videos, an assistive technology should, by default, notify the user that a video exists as this will likely result in the launch of a plug-in. In the case of a video, user agents should indicate what type of video it is, accompanied by any associated alternative equivalent. User agents should prefer plug-ins that support system-specific accessibility features over those that don't. In the case of applets, an assistive technology should, by default, notify the user that an applet exists, as this will likely result in the launch of an associated plug-in or browser specific Java Virtual Machine. In the case of an applet, the notification should include any associated alternative equivalent. This is especially important since applets typically do provide an application frame that would provide application title information. When an applet is loaded, it should support the Java system conventions for loading an assistive technology (refer to the appendix on loading assistive technologies for DOM access). When the applet receives focus, the browser user agent should first notify the user about the applet as described in the previous paragraph and turn control over to the assistive technology that provides access to the Java applet. Suppose an object with a preferred geometry is specified and not rendered, should the alt content be rendered in the preferred (but empty) region? What if the alternative content exceeds the size of the preferred geometry? One option is to allow the user to specify through the UI whether to respect the preferred geometries or ignore them. 3.1.4 Context In addition to providing information about content, user agents must provide contextual information. For example: * table cell row/column position * table cell header information. * Nested list item numbers * Content language User agents can use style sheets (e.g., [CSS2], [XSLT]) to generate contextual information. 3.2 User control of style To ensure accessibility, users must have final control over certain renderings. * For changing text size, allow font size changes or provide a zoom mechanism. * To hide content, use the 'display' and 'visibility' properties of [CSS1]. Implement CSS ([CSS1], [CSS2]) including the CSS2 cascade order and user style sheets. The CSS2 cascade order ensures that user style sheets with "!important" take precedence over author style sheets, giving users final control. Style sheets give authors design flexibility while offering users final control over presentation (refer also to [WAI-WEBCONTENT], checkpoint 3.3). CSS should be implemented by user agents that implement CSS for text that it renders. CSS includes properties for audio, braille (fixed and refreshable), screen, and print rendering, and all relevant properties for supported output media should be implemented. Note that in the CSS cascade order, markup is given less weight than style sheet rules. Thus, an author may use both presentation markup and style sheets, and user agents that support style sheets will prefer the latter. A user style sheet can be implemented through a user interface, which means that the user may not have to understand how to write style sheets; they are generated or the user agent acts as though they were. For an example of this, refer to the style sheets implementation of Amaya ([AMAYA]), which provides a GUI-based interface to create and apply internal style sheets. The same technique could be used to control a user style sheet. For images, applets, and animations: Background images may be controlled by the use of local style sheets, and more effectively if these can be dynamically updated. Animation rate depends on the players used. User agents that provide native rendering of animation (for example a movie player, a driver for animated GIF images, or a java machine) should enable the control of animation rates, or at least allow the user to stop, and to play frame-by-frame, as well as straight rendering. A user agent could provide control of the general timing of a presentation, combined with the ability to select from available tracks manually. An issue to bear in mind is that when animation is synchronized with audio, a user may need the ability to play the animation separately from the associated audio. For time-based presentations: Implement user controls to start, atop, rewind and pause presentations, and where multiple tracks are supported, to choose which tracks should be rendered. SMIL ([SMIL]) provides for a number of these features. A SMIL implementation should provide for direct user control, as well as activation of the controls through a published API, for developers of assistive technologies. For user agents rendering audio: On selecting from among available description tracks. SMIL ([SMIL]) allows users to specify captions in different languages. By setting language preferences in the SMIL player, users may access captions (or audio) in different languages. The G2 player from Real Networks currently allows users to specify which language they prefer, which can be evaluated in a SMIL document to choose from among text or audio tracks. Currently only one language can be indicated which does not permit choosing, for example, English spoken audio with Spanish captions. The Quicktime player currently permits turning on and off any number of tracks individually, which can include audio, video, and text. For user agents rendering video: Implement the CSS positioning and/or SMIL layout languages. Allow the user to freeze a presentation, manually move and resize component video tracks (including captions, subtitles and signed translations) and to apply CSS stylesheets to text-based presentation and SVG. For user agents rendering speech: CSS2 ([CSS2]]) properties for speech can allow users to control speech rate, volume, and pitch. These can be implemented by allowing the user to write and apply a local style sheet, or can be automatically generated by means of (accessible) user controls, which should also be controllable through an API. User interface: * Allow the user to select large or small buttons and controls (and ensure that these values are applied consistently across the user interface) @@CMN: Opera does this.@@ * Allow the user to control features such as menu font sizes, or speech rates - this may be achieved through use of operating system standards. * Allow the user to regroup buttons and controls, and reorder menus. 3.3 Link techniques * Address broken link handling so that it doesn't disorient users. For example, leave viewport as is and notify user. * Provide the user with media-independent information about the status of a link as the link is chosen. For example, do not rely solely on font styles or color changes to alert the user whether or not the link has previously been followed. The user should be able to pick from amongst a list of alert mechanisms (i.e. color changes, sound clips, status line messages, etc.), and should not be limited to only one type of alert mechanism. + For assistive technologies: Provide the user with the option to have the TITLE (if present) or the hyperlink text made available to the user when the user navigates from link to link. * Alert the user if following a link involves the payment of a fee. * When presenting the user with a list of the hyperlinks contained in a document, 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. + Provide the user with orientation information about the listed links. For example, identify a selected link as "Link X of Y", where "Y" is the total number of links available in the document. * Offer the user a list of links which have been visited and a list of links which have not yet been visited, or provide a media-independent mechanism to distinguish between visited and unvisited links. Do _not_ rely on visual or aural prompts alone to signify the difference between visited and unvisited links. * Offer the user a list of links which are internal (i.e., local to document) and those which are external, or provide a media-independent mechanism to distinguish between external and internal links in a list of links. Do not rely on visual or aural prompts *alone* to signify the difference between internal and external links. * Use :before from [CSS2] to clearly indicate that something is a link (e.g., 'A:before { content : "LINK:" }'). * Implement the CSS pseudo-class ':hover'. Lynx allows the user to choose from the following options for images without "alt" specified: * Insert a generic placeholder (e.g., [IMAGE]) in place of the image. * Insert the file name in place of the image. * Render nothing. The same technique might be used when "alt" is specified but whitespace only. However, if an image with unspecified or whitespace "alt" text is part of a link: * Insert a generic placeholder (e.g., [LINK]) in place of the image. * If specified on the link element, render the "title" attribute. * Otherwise, if the link designates an HTML document, use the content of the TITLE element in that document as link text. * Otherwise render the filename or URI of the designated resource. Lynx ([LYNX]) numbers each link and other element and provides information about the relative position of the section of 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. Information about link status and other properties can be provided in an information view such as that provided by Netscape Navigator about how many and what types of elements are in a document. User agents should not consider that all local links (to anchors in the same page) have been visited when the page has been visited. User agents may use graphical or aural icons to indicate visited links or broken links. Users should be able to: * Configure what information about links they wish presented to them. * Turn on and off automatic rendering of this information when a link is focused. * Get information about a focused link on demand, even if automatic rendering has been turned off. 3.4 Table techniques Tables were designed to structure relationships among data. In graphical media, tables are often rendered on a two-dimensional grid, but this is just one possible interpretation of the data. On the Web, the HTML TABLE element has been used more often than not to achieve a formatting effect ("layout tables") rather than as a way to structure true tabular data ("data tables"). Layout tables cause problems for some screen readers and when rendered, confuse users. Even data tables can be difficult to understand for users that browse in essentially one dimension, i.e. for whom tables are rendered serially. The content of any table cell that visually wraps onto more than one line can be a problem. If only one cell has content that wraps, there is less problem if it is in the last column. Large tables pose particular problems since remembering cell position and header information becomes more difficult as the table grows. User agents facilitate browsing by providing access to specific table cells and their associated header information. How headers are associated with table cells is markup language-dependent. Tabular navigation is required by people with visual impairments and some types of learning disabilities to determine the content of a particular cell and spatial relationships between cells (which may convey information). If table navigation is not available users with some types of visual impairments and learning disabilities may not be able to understand the purpose of a table or table cell. 3.4.1 Table rendering A linear view of tables -- cells presented row by row or column by column -- can be useful, but generally only for simple tables. Where more complex structures are designed, allowing for the reading of a whole column from header downward is important as is carrying the ability to perceive which header belongs to which column or group of columns if more than one is spanned by that header. It is important for whole cells to be made available as chunks of data in a logical form. It might be that a header spans several cells so the header associated with that cell is part of the document chunk for that and each of the other cells spanned by that header. Inside the cell, order is important. It must be possible to understand what the relationships of the items in a cell are to each other. Properly constructed data tables generally have distinct TH head cells and TD data cells. The TD cell content gains implicit identification from TH cells in the same column and/or row. For layout tables, a user agent can assist the reader by indicating that no relationships among cells should be expected. Authors should not use TH cells just for their formatting purpose in layout tables, as those TH cells imply that some TD cells should gain meaning from the TH cell content. When a table is "read" from the screen, 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. If read directly from the screen, this table might be rendered as "This is the top left cell This is the top right cell", which would be confusing to the user. A user agent should provide a means of determining the contents of cells as discrete from neighboring cells, regardless of the size and formatting of the cells. This information is made available through the DOM [DOM1]). 3.4.2 Cell rendering Non-graphical rendering of information by a browser or an assistive technology working through a browser will generally not render more than a single cell, or a few adjacent cells at a time. Because of this, the location of a cell of interest within a large table may be difficult to determine for the users of non-graphical rendering. In order to provide equivalent access to these users, compliant browsers should provide a means of determining the row and column coordinates of the cell having the selection via keyboard commands. Additionally, to allow the user of a non-graphical rendering technology to return to a cell, the browser should allow a means of moving the selection to a cell based on its row and column coordinates. At the time the user enters a table, or while the selection is located within a table, the user agent should allow an assistive technology to provide information to the user regarding the dimensions (in rows and columns) of the table. This information, in combination with the summary, title, and caption, can allow the user with a disability to quickly decide whether to explore the table of skip over it. Dimensions is an appropriate term, though dimensions needn't be constants. For example a table description could read: "4 columns for 4 rows with 2 header rows. In those 2 header rows the first two columns have "colspan=2". The last two columns have a common header and two subheads. The first column, after the first two rows, contains the row headers. Some parts of a table may have 2 dimensions, others three, others four, etc. Dimensionality higher than 2 are projected onto 2 in a table presentation. The contents of a cell in a data table are generally only comprehensible in context (i.e., with associated header information, row/column position, neighboring cell information etc.). User agents provide users with header information and other contextual information. Techniques for rendering cells include: * Provide this information through an API. * Render cells as blocks. This may assist some screen readers. Using this strategy, the user agent might render individual cells with the relevant top and side headers attached. * Allow navigation and querying of cell/header information. When the selection is on an individual cell, the user would be able to use a keyboard command to receive the top and left header information for that cell. The user agent should appropriately account for headers that span multiple cells. * Allow users to read one table column or row at a time, which may help them identify headers. * Ignore table markup entirely. This may assist some screen readers. However, for anything more than simple tables, this technique may lead to confusion. 3.4.3 Cell header algorithm User agents should use the algorithm to calculate header information provided in the HTML 4.0 specification ([HTML40], section 11.4.3). Since not all tables are designed with the header information, user agents should provide, as an option, a "best guess" of the header information for a cell. Note that data tables may be organized top-to-bottom, bottom-to-top, right-to-left, and left-to-right, so user agents should consider all edge rows when seeking header information. Some repair strategies for finding header information include: * Consider that the top or bottom row to 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. The user may choose the form and amount of this information, possibly announcing the row heads only once and then the column head or its abbreviation ("abbr") to announce the cell content. Issues to consider: 1. TH cells on both the left and right of the table need to be considered. 2. 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. 3. 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. 4. Finding column header cells assumes they are all above the TD cell to which they apply. 5. A TH with "colspan" set needs to be included in the list of TH for the M-1 columns to the right of the column in which the TH is found. 3.4.4 Table metadata Users of screen readers or other serial access devices cannot easily glean information about a page "at a glance". This is particularly difficult when accessing two-dimensional tables and trying to determine their content. Therefore, contextual information about tables (available from author-supplied markup or generated by the user agent) is very important to making them accessible. Text metadata about tables can come from a number of elements, attributes, the structure of the table itself, or other sources. Useful information to make available to users includes: * The number of column groups and columns. * The number of row groups and rows, in particular information about table headers and footers. * 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. * The row/column dimensions of the table. 3.5 Frame techniques Frames were originally designed for use by graphical user interfaces to allow the graphical viewport to be broken up into pieces that could change independently (e.g,. selecting an entry in a table of contents in one frame changes the contents of a second frame). However Frames can pose problems users who rely on synthesized speech, refreshable braille, and magnified views. Problems include: * Orientation: What frame am I in? How is the frameset organized? What is the relationship among frames? What happens in frame B when I select a link in frame A? * Navigation: How do I get from frame to frame? To help users, user agents should: * Consider the author's alternative presentation to frames (e.g., provided by NOFRAMES in [HTML40]). * Inform the user that they are viewing a frameset. * Provide information about the number of frames in the frameset. * Provide (possibly nested) lists of links to each frame in the frameset. The link text can be the frame title (given by "title" or "name" if "title" is not present). Or, if no title or name are available, render the title (e.g., the TITLE element in HTML) of the document that is loaded into the frame. Other alternative renderings for a frameset include simply rendering each frame in the frameset sequentially as a block (e.g., aligned vertically in a graphical environment). * Highlight the current frameset (e.g., with a thick border, by displaying the name of the current frameset in the status bar, etc. * Provide information about the current frame. Make available frame title for speech synthesizers and braille devices. * If a page does not have a list of links within in a frame available outside the frame, make the list available outside the frame. * 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 alternative content. * Allow the user to bookmark the current frame. * Inform the user if an action in one frame causes the content of another frame to change. Allow the user to navigate quickly to the frame(s) that changed. To name frames in HTML, use: 1. The "title" attribute on FRAME, or if not present, 2. The "name" attribute on FRAME, or if not present, 3. Title information of the referenced frame source (e.g., the TITLE element of the source HTML document), or 4. Title information of the referenced long description (e.g., what "longdesc" refers to in HTML), or 5. Frame context (e.g., "Frame 2.1.3" to indicate the path to this frame in nested framesets). Frame structure information should be available through the DOM and appropriate accessibility interfaces. Using DOM and operating specific accessibility API to expose frame information provides one means for assistive technologies to provide alternative control of frames and rendering of frame information. The user agent should fully implement the DOM Level 1 Recommendation ([DOM1]) API related to frames: HTMLFrameSetElement, HTMLFrameElement, and HTMLIFrameElement. For people with visual impairments who are enlarge text on the screen to improve readability, frames become distorted and unusable. Other users with cognitive disabilities sometimes become disoriented in complex side-by-side frame configurations. To improve access to frames, user agents should allow frames to be viewed as a list so the user can identify the number of frames and the functions of each frame. If no frames information is present it should also be rendered so the user can optionally use that view of the information. 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 illustrate how some user agents handle this frameset. First, rendering in Microsoft Internet Explorer 5.0 on a Windows platform: Image shows the example frameset with five frame panes rendered in Microsoft Internet Explorer 5.0 Rendering by Lynx on Linux: 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 on Windows: Image shows the example frameset with five links for each of the frame elements in IBM home page reader Audio rendering by Home Page Reader on Windows: @@add here@@ 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 snapshot, the menu bar indicates the number of frames and a check next to the name of the frame element indicates which is the current frame: Image shows 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 3.6 Form techniques For labels explicitly associated with form controls (e.g., "for" attribute on LABEL in HTML), make available label information when the user is navigating among the form controls. This information must be provided in a device-independent manner, and the user should be able to choose from a list of mechanisms that provide access to the content of the label. For semantic information explicitly associated with groupings of form controls (e.g., groupings of radio buttons or checkboxes contained in a FIELDSET), make available the information contained in the LEGEND defined for the FIELDSET to the user. This information must be provided in a device-independent manner, and the user should be able to choose from a list of mechanisms that provide access to the content of the LEGEND. Provide information about the percentage of form that has already been filled out as the user moves through the form controls. This information must be provided in a device-independent manner. The user should also be able to query the user agent through a simple, well-documented mechanism (such as a keystroke or keystroke combination) to learn what percentage of the form has been completed. Allow the user to know what percentage of a form has been completed as the user navigates the form. will help users avoid prematurely submitting an incomplete form. This is particularly important for anyone moving through a form serially; users who encounter a submit button usually think this means the end of a form, but it may not be. (Refer also to the technique detailing methods of providing users with orientation information about individual form controls when a form control receives focus for a more detailed discussion of this issue.) Provide the user with orientation information about a form. Users should be able to query the user agent for: * the presence of a form -- the user should be able to query to user agent for the presence of a form within the document being rendered. Some user agents (such as Opera and Netscape Navigator) already indirectly provide such functionality in a non-interactive manner, through the provision of "form navigation" keyboard commands. When invoked, these "form navigation" commands move the user agent's focus to the first form field contained in the document currently being rendered (provided, of course, that the document contains a form. Although providing discrete "form navigation" commands allows users to quickly move to the first form field within a document, users need to be explicitly notified if the document does not contain a form. Such notification should be conveyed in a device-independent manner, and the user should not be limited to one means of notification (i.e., display a message on the status bar and play a sound). * the number of forms in a document Provide the user with orientation information about individual form controls when a form control receives focus. For example, the most basic orientation information would be to identify the form control with focus as "Field X of Y", where "Y" is the total number of fields contained in the form. This will help prevent users accessing the form serially (such as a blind user using a screen reader or someone using a voice browser over a phone) from prematurely invoking the form's submit mechanism. It is a common practice for forms (particularly those used to query search engines) to be laid out visually, so that the submit and reset buttons (if present) immediately follow a text-entry field, despite the presence of other form controls (such as radio buttons and checkboxes) within the FORM element. A user accessing such a form in a serial manner, therefore, is likely to mistake the submit button for the end of the form, and activate it, unaware that it is followed by further form controls which could -- in the example of a search engine query submission form -- prove an invaluable aid in tailoring the content being submitted via the form. Use of such orientation information (i.e., "Field X of Y" or the percentage of the form completed) will also decrease the amount of time needed to submit the form (a crucial consideration when forms are being used to facilitate bidding for online auctions) as well as reduce the frustration of the end user, who, due to the visually oriented layout of the form, is confused when the submission of the form repeatedly leads to a message such as "Form Incomplete - Use your browser's back button to return to the form". When a document contains more than one form, form control orientation information should also include data which will identify to which form the form control with focus belongs. Notification could take the form: Form Z: Field X of Y where "Z" identifies the form, "X" the form field with focus an "Y" the total number of form fields contained in "Form Z". Provide more detailed orientation information pertaining to form: * When a grouping of radio buttons receives focus, identify the radio button with focus as "Radio Button X of Y", where "Y" represents the total number of radio buttons in the grouping. HTML 4.0 ([HTML40]) specifies the FIELDSET element, which allows authors to group thematically related controls and labels. The LEGEND element assigns a caption to a FIELDSET. If a LEGEND has been defined for the grouping of radio boxes, use the information contained within the LEGEND to more precisely identify the number of radio buttons in the grouping. For example, if the LEGEND element has been used to identify a FIELDSET of radio buttons, each of which has a LABEL associated with it, as "Connection Rate", identify the radio button as it receives focus 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 associated with the radio button with focus. * Provide information about what is required for each form control. GUI browsers, for example, could convey such information via context- sensitive help. 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) Hit 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/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). For more information, please refer to the following technique. Allow the user to invoke an external editor when a TEXTAREA receives focus. A user may wish to use an external editor, rather than enter text directly in a TEXTAREA for myriad reasons, including: * the ability to more efficiently and expeditiously review the text being input * the ability to spell check the text being input * the ability to use macros or other special features of the external editor, including the ability to increase the contrast between foreground and background colors, access to a wider range of screen-display fonts, etc. * the ability to save a local copy of the text being input * the user's familiarity with the external editor will encourage the user to actually enter text into a TEXTAREA--an exercise which is often an extremely daunting task, given the limitations imposed by the physical dimensions of the TEXTAREA. A user will also find it much easier to review what he or she has typed when using an external editor. Provide information about the order of form controls (e.g., as specified by "tabindex" in HTML). This is important since: * most forms are visually oriented, employing changes in font size and color * users who access forms serially need to know they have supplied all the necessary information before submitting the form. Provide information about required fields. Since authors often use color changes, font styling, or a graphical symbol alone to express that a field is required, the user should be able to configure the user agent so that it alerts him that the field is required for submission of the form content. Strategies for achieving this include: * Allow the user to view a list of required form fields. Such a list should be invokable via a simple and well documented keybinding. * Allow the user to define an alert mechanism (such as the playing of a sound) which will be invoked when a required field receives focus. The user should be able to pick from amongst a list of alert mechanisms (i.e. color or font-style changes to the field label, the playing of a sound clip, a status line message, etc.), and should not be limited to only one type of alert mechanism. Do not rely on visual or aural prompts alone to signify a required form field. Allow the user to configure the user agent so that SELECT form fields which use the "multiple" attribute to allow the end user to select more than one OPTION can be transformed into a list of checkboxes. * Preserve the LABELs set for the OPTGROUP and each individual OPTION, and re-associate them with the user agent generated checkboxes. The LABEL defined for the OPTGROUP should be converted into a LEGEND for the resultant FIELDSET, and each checkbox should retain the LABEL defined for the corresponding OPTION. * Note. Lynx automatically transforms SELECT form fields which use the "multiple" attribute to allow the end user to select more than one OPTION into checkboxes. Allow the user to configure the user agent sot that SELECT form fields can be transformed into a list of radio buttons. * Any such transformation should retain the accessibility information defined for the original form controls. * Note. Lynx provides this functionality as a configurable option, which can be changed on-the-fly while a page is being rendered. To promote the comprehensibility of the transformed output for users using screen-readers and refreshable Braille displays, Lynx places each OPTION that it transforms into a radio button on a separate line. 3.6.1 Form submission techniques Users (notably users with blindness or any user unaccustomed to online forms) do not want forms to be submitted without their consent, e.g., when submitted through scripts. In this case user agents should request confirmation before submitting the form content. Nor do they wish to be prompted before each form submission when they have explicitly submitted the form (e.g., through the standard submit button). Inadvertently pressing the RETURN or ENTER key is quite a prevalent phenomenon among users of every level of expertise - especially those who often find it necessary to switch between user agents. Lynx, for example, uses the ENTER key within FORMs as a means of exposing drop-down (or pop-up, depending upon your point of view) SELECT menus. Thus, when one encounters a SELECT menu using Lynx, one: exposes the content of the menu by pressing the ENTER key, and then is able to navigate between OPTIONs using the up and down arrows or via Lynx's text-search feature. When one finds the appropriate OPTION, it is selected by pressing ENTER, which causes the selected item to be displayed in the SELECT menu listbox. The problem posed by the default "submit on enter" feature of most GUI browsers is not limited to the SELECT menu problem outlined above. Lynx (as well as several other text-based browsers) uses the ENTER/RETURN key as a means of toggling several FORM controls, such as the selection of checkboxes and radio buttons. Speech users may be frustrated and misdirected by the use of javascript and event handler controlled pseudo-forms, wherein the user is presented with a menu (in the form of a listbox in GUI browsers), and is redirected to a different viewport upon selection of an OPTION. The markup behind such pseudo-forms is a mix of javascript (in particular the "function switchpage(select)" command) and HTML FORM controls, which utilize HTML4's event handler script attributes (in particular the "onchange" event handler attribute has been defined. An example (gleaned from the document source for one Web site follows: