User Agent Accessibility Guidelines 1.0
W3C Working Draft 5-October-1999
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- Jon Gunderson <firstname.lastname@example.org>
Ian Jacobs, W3C
Copyright © 1999 W3C®
Keio), All Rights Reserved. W3C
licensing rules apply.
This document provides guidelines to
user agent developers for making
their products -- browsers, multimedia players, plugins -- accessible
to people with disabilities. An accessible user agent allows users
with disabilities to retrieve and view Web resources or to enable
access when used in conjunction with other software or hardware,
called assistive technologies.
These guidelines discuss the accessibility of the user agent as well
as communication with assistive technologies such as screen
readers, screen magnifiers, braille displays, and voice input
An appendix to this document summarizes the requirements for
accessibility and may be used by developers as a checklist for
satisfying the guidelines. The checklist is available both as a tabular
summary and as a simple list.
A separate document, entitled "Techniques for User Agent Accessibility Guidelines 1.0" ([UA-TECHNIQUES]), suggests techniques
for satisfying each requirement. The Techniques Document has been
designed to track changes in technology and implementation solutions
and is expected to be updated more frequently than the current
"User Agent Accessibility Guidelines 1.0" is part of a series of accessibility guidelines
published by the Web Accessibility
Initiative (WAI) . The series also includes "Web Content Accessibility
Guidelines 1.0" ([WAI-WEBCONTENT])
and "Authoring Tool Accessibility Guidelines 1.0" ([WAI-AUTOOLS]).
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
In this version of the document, the conformance distinction
between "graphical desktop user agents" and "dependent user agents"
was removed. However, the Working Group has not yet decided how to
modify those checkpoints that were designated "for dependent user
Please send comments about this document to the public mailing list:
This document has been produced as part of the
Web Accessibility Initiative, and is intended as
a draft of a Proposed Recommendation for how to improve user agent
accessibility. The goals of the WAI UA
Working Group are discussed in the WAI UA
charter. A list of
the UA Working Group participants is
A list of current W3C Recommendations and other technical documents
can be found at http://www.w3.org/TR.
For those unfamiliar with accessibility issues pertaining to
user agent design, consider that many users may be accessing
the Web in contexts very different from your own:
- They may not be able to see, hear, move, or
may not be able to process some types of
information easily or at all.
- They may have difficulty reading or comprehending text.
- They may not have or be able to use a keyboard or mouse.
- They may have a text-only screen, a small screen, or
a slow Internet connection.
- They may not speak or understand fluently
the language in which content is written or spoken.
- They may be in a situation where their eyes, ears, or
hands are busy or interfered with (e.g., driving to work,
working in a loud environment, etc.).
User agents must be designed to take into account the diverse
functional requirements of users with disabilities. Software that
follows the guidelines in this document will not only benefit users
with disabilities, it will be more flexible, manageable, and
extensible. The guidelines have been chosen according to some basic
principles of accessible design, presented below.
This document is organized according to several principles that
will improve the design of any type of user agent:
The user must have access to the functionalities offered by the
user agent through its user interface. Access must be possible
through all supported input and output application programming interfaces
This includes access to
functionalities built into the tool (made available through menus,
dialogs, toolbars and other user interface components) as well as
those offered via the Web resource (made available through links, form
controls, applets, and other active elements).
User agents should provide access to functionalities in different
ways to meet the skills and needs of different audiences:
- Contextual access
(e.g., through cascading menus, through help systems, etc.)
helps users with cognitive impairments and any users
unfamiliar with the tool.
- Direct access (e.g., through keyboard or voice shortcuts)
helps some users with motor limitations and speeds up
use by experienced users.
The general topic of user interface accessibility for computer
software exceeds the scope of this document. The guidelines do discuss
some important user interface topics such as device-independence,
configurability, and accessible product documentation. Software
developers should also remember that user interfaces must be
intuitive, simple, and tested. Features that are known to promote
accessibility should be made obvious to users and easy to find. The
Techniques Document ([UA-TECHNIQUES])
includes some references to general software accessibility guidelines.
User agents most ensure access to content:
- By ensuring access to all text, video, sound, and other content,
including alternative content
(e.g., "alt" attribute values in HTML, external long descriptions, etc.).
- By allowing users to control content rendering parameters
(text size, colors,
synthesized speech rate and volume, etc.).
- By allowing users to navigate the content (e.g., with scrollbars,
navigation of active elements, structured views, etc.).
- By making information available to
dependent user agents
through standard APIs.
User agents can help the user remain oriented in a page
or site by supplying context, including:
- Browsing context. It helps users greatly to know
the number of frames, the
title of the current frame, whether loading for a
page or video clip has finished or stalled, etc.
Graphical clues about browsing context
such as frames, proportional scroll bars, a
visually highlighted selection, etc.
help some, but not all users, so the information must be
available in a device-independent manner.
- Element context. For instance,
users with blindness who navigate by surfing only the links
of a page or presentation benefit from information that will help them decide
quickly whether to follow the link: whether the link has already
been visited, the type of the target resource, the length of an
audio or video clip that will be started, whether the link involves
a fee, etc.
- Summary information about specific elements (e.g.,
the dimensions of a table, the length of an audio clip,
the structure of a form, etc.)
The user agent should also minimize the chances the
user will become disoriented. User agents should:
- For changes to the content or viewport that the
user does not initiate, allow the user to request
notification of these changes. (e.g.,
when a window opens, a script is executed, etc.).
- Allow the user to return to known states. The "back"
functionality is a valuable "undo" tool for returning to
a known state.
Following system standards and conventions promotes accessibility
in a number of ways:
- Observing system conventions in
user interface design, software installation,
and software documentation improves usability.
- Using standard system interfaces makes it possible
for assistive technologies to access information predictably.
Communication through standard interfaces is particularly important
for graphical desktop browsers, which must make information available
to dependent user agents. Even when a
user agent implements a feature natively, it should make relevant
information available through standard interfaces. This will benefit
assistive technologies, scripting tools, and automated test engines.
It will also will promote modularity and software reuse.
The twelve guidelines in this document
state general principles for the development of accessible user
agents. Each guideline includes:
- The guideline number.
- The statement of the guideline.
- Guideline navigation links. Three links allow
navigation to the next guideline (right arrow
icon), the previous guideline (left arrow icon),
or the current guideline's position in the table
of contents (up arrow icon).
- The rationale behind the guideline and some
groups of users who benefit from it.
- A list of checkpoint definitions.
The checkpoint definitions in each
guideline explain how the guideline applies to particular user agent
features or behavior. Each checkpoint definition includes:
- The checkpoint number.
- The statement of the checkpoint.
- The priority of the checkpoint. Priority 1
checkpoints are highlighted through the use of style sheets.
- Optional informative notes, clarifying examples,
and cross references to related guidelines or checkpoints.
- A link to a relevant entry in the
"Checkpoint Map" of the Techniques Document
(refer to [UA-TECHNIQUES]).
The Checkpoint Map lists each checkpoint and links
to the sections of the Techniques
Document where the checkpoint is discussed in detail,
including information about implementation and examples.
Each checkpoint is intended to be
specific enough so that someone reviewing a user
agent may verify that the checkpoint has been satisfied.
The following editorial conventions are used throughout
- Element names are in uppercase letters.
- Attribute names are quoted in lowercase letters.
- Links to definitions are highlighted through
the use of style sheets.
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
- [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.
The terms "must", "should", and "may" (and related terms) are used
in this document in accordance with RFC 2119 ([RFC2119]).
User agents must satisfy natively all the
applicable checkpoints for a chosen
This section defines three levels of conformance to this
- Conformance Level "A":
all Priority 1 checkpoints are satisfied
- Conformance Level "Double-A":
all Priority 1 and 2 checkpoints are satisfied
- Conformance Level "Triple-A":
all Priority 1, 2, and 3 checkpoints are satisfied
Note. Conformance levels are spelled out in text
so they may be understood when rendered as speech.
Claims of conformance to this document must use one of the
following two forms.
Form 1: Specify:
- The guidelines title: "User Agent Accessibility Guidelines 1.0"
- The guidelines URI: http://www.w3.org/WAI/UA/WAI-USERAGENT-19991005
- The conformance level satisfied: "A", "Double-A", or "Triple-A".
Example of Form 1:
This product conforms to W3C's "User Agent Accessibility Guidelines 1.0",
available at http://www.w3.org/WAI/UA/WAI-USERAGENT-19991005, level Double-A.
Form 2: Include, on product packaging or documentation, one of three
icons provided by W3C and for Web documentation, link the icon to the
appropriate W3C explanation of the claim.
Note. In the event this document becomes a W3C
Recommendation, information about the icons and how to use them will
be available at the W3C Web site.
Since not all users make use of the same hardware for
input or output, software must be designed to work
with the widest possible range of devices. For instance,
not all users have pointing devices, so software
must not rely on them for operation. Users must be
able to reach all functionalities offered by the user
agent interface with all input device APIs supported by
the underlying system.
The best way to make this possible is to design software
that follows system conventions and uses standard
for user input and output. When user agents use these
standard interfaces, other software can
programmatically trigger mouse or keyboard events. For
instance, some users who may not be able to enter text easily
through a standard physical keyboard can still use voice
input, an on-screen keyboard, or other special
devices to operate the user agent.
Since not all users have speakers or the ability to hear, software
must not rely on audio output alone for messages and alerts. Any
output provided in audio should also be available through other means
(e.g., visual flashes for beeps, text messages for spoken messages, etc.).
Text is perhaps the most accessible output medium, since most alternative
output mechanisms rely on the presence of system-drawn text on the
Standard interfaces make it possible for users to use
a variety of input and output devices,
including pointing devices, keyboards,
braille devices, head wands, microphones, touch
screens, speech synthesizers, and more.
Please refer also to guideline 6, which discusses the
importance to accessibility of following operating system conventions.
- 1.1 Ensure that all functionalities offered through the user interface may be operated through standard input device APIs supported by the operating system. [Priority 1]
- 1.2 Ensure that the user can interact with all active elements in a device independent manner. [Priority 1]
- For example, ensure that the user can activate
links of a client-side image map in a device-independent
manner (e.g., by making them available as text links).
- 1.3 Ensure that the user can install the user agent software in a device independent manner. [Priority 1]
- 1.4 Ensure that the user can configure the user agent in a device independent manner. [Priority 1]
- 1.5 Ensure that the user can access user agent documentation in a device independent manner. [Priority 1]
- 1.6 Ensure that all messages to the user (e.g., warnings, errors, etc.) are available through standard output device APIs supported by the operating system. [Priority 1]
For instance, ensure that information about how
much of a page or video clip has been viewed is available
through output device APIs. Proportional navigation bars
may provide this information visually, but the information
must be available to users relying on synthesized speech or braille
Ensuring access to user agent functionality through the system's
standard keyboard API (where available) is important to accessibility
since keyboard access is available to many users and is widely
supported. Even when a user doesn't use a physical keyboard, it is
still possible to simulate keyboard events with software. This
guideline is important for ensuring compatibility between
graphical desktop browsers and
dependent user agents.
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 system conventions,
author-specified shortcuts, and user preferences. The user agent's
default configuration should include shortcuts for frequently
performed actions and should respect system conventions.
The more apparent the keyboard commands are to all users, the more
likely it is that new users with disabilities will find them and use
them. Refer also to checkpoint 9.12.
Checkpoints in this section do not apply to user agents (e.g.,
kiosks) that do not natively support keyboard input.
- 2.1 By default and without additional customization, ensure that all functionalities offered by the user agent may be operated through the standard keyboard API supported by the operating system. [Priority 1]
- Note. Functionalities include
being able to show, hide, resize and move graphical
created by the user agent.
- 2.2 Provide documentation on default keyboard commands and include with user agent documentation and/or user help system. [Priority 1]
- Refer also to guideline 12.
- 2.3 Provide information to the user about the current keyboard configuration. [Priority 1]
- Note. For example,
users should be able to find information about
complex key combinations. Refer also to guideline 12.
- 2.4 Allow the user to configure the keystrokes used to activate user agent functionalities. Users should be able to configure single key activation of functionalities. [Priority 2]
- 2.5 Allow the user to turn on and off author-specified keyboard configurations. [Priority 2]
- For example, in HTML, the author may specify
tabbing order with the "tabindex" attribute and
keyboard bindings with the "accesskey" attribute.
- 2.6 Use platform conventions to indicate which keys activate which user agent functionalities. [Priority 2]
- For example, on some platforms,
if a functionality is available from a menu, the
letter of the key that will activate that functionality is
- 2.7 Avoid default keyboard configurations that interfere with system conventions. [Priority 2]
For example, the default configuration should not include
"Alt-F4" or "Control-Alt-Delete" on 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 6.
- 2.8 Provide a default keyboard configuration for frequently performed operations. [Priority 3]
Users may not be able to perceive primary content due to a
disability or a technological limitation or configuration (e.g., browser
to display images). Markup languages may provide a number of
mechanisms for specifying alternative representations of content:
through attribute values, element content, or in separate
resources. User agents must also take into account markup related
to natural language rendering, using appropriate fonts, text
directionality, and synthesized speech elements.
In dynamic presentations such as synchronized multimedia
presentations created with SMIL (refer to [SMIL]), content changes over time. Users with
cognitive or physical disabilities may not be able to interact with a
presentation within the time frames designed by the author. To ensure
that a presentation remains accessible, user agents rendering
synchronized presentations must either provide access to content in a
time-independent manner or allow users to control the playback rate of
the presentation. For information about SMIL accessibility,
please refer to [SMIL-ACCESS].
User agents should allow users to specify whether
primary content should be rendered, or alternative
equivalents supplied by the author, or both. 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.
- 3.1 Ensure that the user has access to all content, including alternative representations of content. [Priority 1]
- Mechanisms for specifying alternative content
vary according to markup language. For instance, in
HTML or SMIL, the "alt" attribute specifies alternative
text for many elements. In HTML, the content of the OBJECT
element is used to specify alternative content,
the "summary" attribute applies to tables, etc.
- 3.2 For dependent user agents only. Ensure that the user has access to the content of an element selected by the user. [Priority 1]
- For instance, allow the user to identify a table cell
with the selection and provide the user with cell content
and (optionally) associated header information.
Refer also to checkpoint 8.1 and checkpoint 6.2.
- 3.3 Render content according to natural language identification. For unsupported natural languages, notify the user of language changes when configured to do so. [Priority 1]
Natural language may be identified by markup (e.g., the "lang"
attribute in HTML or "xml:lang" in XML) or HTTP headers.
Refer also to checkpoint 6.2.
- 3.4 Provide time-independent access to time-dependent active elements or allow the user to control the timing of changes. [Priority 1]
- 3.5 When no alternative text representation has been specified, indicate what type of object is present. [Priority 2]
- 3.6 When alternative text has been specified explicitly as empty (i.e., an empty string), render nothing. [Priority 3]
Checkpoints for continuous equivalent tracks
(closed captions, auditory descriptions, etc.):
- 3.7 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]
- 3.8 If a technology allows for more than one continuous equivalent tracks (e.g., closed captions, auditory descriptions, video of sign language, etc.), allow the user to choose from among the tracks. [Priority 1]
Checkpoints for audio:
- 3.9 If a technology allows for more than one audio track, allow the user to choose from among tracks. [Priority 1]
Some rendering behavior may make the user agent unusable or may
obscure information. For instance, people with photosensitive epilepsy
must be able to turn off flashing within certain ranges, otherwise the
flashing may trigger a seizure. Blinking can affect screenreader
users, since screenreaders (in conjunction with speech synthesizers or
braille displays) may repeat the text every time it blinks. Users who
require specific color contrasts or who have low vision need to be
able to turn off background images if those images interfere with
their ability to read text.
Users may need to turn off author style sheets if they
cannot override them with their own style preferences.
Dynamically changing web content, scripts that open windows,
automatically forwarded or refreshed pages, and similar changes
unanticipated by the user may disorient some users with cognitive
disabilities and may cause problems for some dependent user agents.
Please also refer to guideline 5 and guideline 11.
- 4.1 Allow the user to turn on and off rendering of images. [Priority 1]
- 4.2 Allow the user to turn on and off rendering of background images. [Priority 1]
- 4.3 Allow the user to turn on and off rendering of video. [Priority 1]
- 4.4 Allow the user to turn on and off rendering of sound. [Priority 1]
- 4.5 Allow the user to turn on and off rendering of continuous equivalent tracks (e.g., closed captions, auditory descriptions, video of sign language, etc.) [Priority 1]
- 4.6 Allow the user to turn on and off animated or blinking text. [Priority 1]
- 4.7 Allow the user to turn on and off animations and blinking images. [Priority 1]
- 4.8 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.
- Note. Users should be able,
for security reasons, to prevent scripts from executing on their
- 4.9 Allow the user to turn on and off support for user style sheets. [Priority 1]
- 4.10 Allow the user to turn on and off support for author style sheets. [Priority 1]
- 4.11 Allow the user to turn on and off support for spawned windows. [Priority 1]
- 4.12 Allow the user to choose between a frameset or its alternative supplied by the author. [Priority 2]
For example, in HTML, allow the user to choose between a frameset or a
NOFRAMES alternative. The ability to control frames is important for
users with screen readers and users with some cognitive impairments.
- 4.13 Allow the user to turn on and off author-specified page forwards that occur after a time delay and without user intervention. [Priority 3]
For example, when turned off,
offer a static link to the target resource instead.
- 4.14 Allow the user to turn on and off automatic page refresh. [Priority 3]
For example, when turned off,
allow the user to refresh the page manually
instead (through the user interface).
In order to access content, some users may require that it be
rendered in a manner other than what the author intended. Users with
visual impairments, including color blindness, may be insensitive to
certain colors and may not be able to perceive author-specified or
user agent default color combinations. Users with reduced visual
acuity, including people who are older, may require larger text than
user agent defaults or the text size specified by the author.
User agents must therefore allow the user to control:
- Style parameters (e.g., text size, colors, audio volume,
speech pitch, video frame rate, etc.). Style information
includes author-specified styles and user agent defaults.
- Aspects of the user interface. User agents must ensure access
to selection and focus information and allow users to be
notified of and to control author-specified changes
to the browsing context that may make content inaccessible.
Note. The checkpoints in this guideline apply to
all content, in including alternative representations of content.
Refer also to guideline 11.
Checkpoints for fonts and colors:
- 5.1 Allow the user to control font family. [Priority 1]
- 5.2 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.
- 5.3 Allow the user to control foreground color. [Priority 1]
- 5.4 Allow the user to control background color. [Priority 1]
- 5.5 Allow the user to control selection highlighting (e.g., foreground and background color). [Priority 1]
- 5.6 Allow the user to control focus highlighting (e.g., foreground and background color). [Priority 1]
Checkpoints for applets and animations:
- 5.7 Allow the user to control animation rate. [Priority 2]
Checkpoints for video.
- 5.8 Allow the user to control video frame rates. [Priority 1]
- 5.9 Allow the user to control the position of audio closed captions. [Priority 1]
- 5.10 Allow the user to start, stop, pause, and rewind video. [Priority 2]
Checkpoints for audio:
- 5.11 Allow the user to control audio playback rate. [Priority 1]
- 5.12 When the user agent renders audio natively, allow the user to control the audio volume. [Priority 2]
- 5.13 Allow the user to start, stop, pause, and rewind audio. [Priority 2]
Checkpoints for synthesized speech:
- 5.14 Allow the user to control synthesized speech playback rate. [Priority 1]
- 5.15 Allow the user to control synthesized speech volume. [Priority 1]
- 5.16 Allow the user to control synthesized speech pitch, gender and other articulation characteristics. [Priority 2]
Checkpoints for changes to the user interface:
- 5.17 When new windows or user interface components are spawned, allow the user to control window size and position. [Priority 2]
To promote interoperability, user agents should adopt operating
system conventions and standard APIs for communication, user interface
design, documentation, etc. Following operating system conventions and
implementing standard APIs will promote predictability for users as
well as dependent user agents that
rely on information from other software.
Some operating systems have operating system-level flags and
settings that are pertinent to accessibility, such as high-contrast
colors and "show" sounds for people with hearing impairments. User
agents should take these global settings into account for their own
- 6.1 Use and provide accessible interfaces to other technologies. [Priority 1]
- To promote interoperability, open standards and W3C
specifications should be used wherever possible.
- 6.2 Provide programmatic read and write access to user agent functionalities and user interface controls (including selection and focus) by using operating system and development language accessibility resources and conventions. [Priority 1]
- 6.3 Notify dependent user agents of changes to content and user interface controls (including selection and focus) by using operating system and development language accessibility resources and conventions. [Priority 1]
- 6.4 Comply with W3C Document Object Model specifications and export interfaces defined by those specifications. [Priority 1]
- For example, refer to [DOM1]. User agents should
export these interfaces using available system conventions.
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."
- 6.5 Provide programmatic exchange of information in a timely manner. [Priority 2]
- This is important
for synchronous alternative renderings and simulation of events.
- 6.6 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 2.7.
W3C specifications promote interoperability, which improves
accessibility through predictability and openness. The current
guidelines also recommend support for W3C specifications (e.g., HTML,
CSS, MathML, SMIL, etc.) for the following reasons:
- W3C specifications include "built-in" accessibility features.
- W3C specifications undergo early review to ensure that accessibility
issues are considered during the design phase.
- W3C specifications are developed in an open, industry consensus process.
- 7.1 Implement the accessibility features defined for supported specifications. [Priority 1]
- Note. The
Techniques Document ([UA-TECHNIQUES])
discusses accessibility features of W3C specifications.
- 7.2 Support appropriate W3C Recommendations. [Priority 2]
- For instance, for marking up Web pages,
support HTML or an XML application; for style sheets, support CSS; for
mathematics, support MathML; for synchronized multimedia,
support SMIL, etc.
Refer also to checkpoint 6.4.
Navigation mechanisms help all users find the information they
seek. User agents should provide a variety of mechanisms - from
simple scrolling through content to search mechanisms to serial
("tabbing") navigation - to meet the diverse needs of users, in
particular users of devices that render content serially (e.g.,
synthesized speech output or single-line refreshable braille
displays). So that users of serial devices are not required to
view an entire page or presentation to find information, user agents should
provide more direct navigation mechanisms.
Authors are encouraged to include navigation mechanisms (e.g.,
image maps or navigation bars) designed for their content, but user
agents should provide generic mechanisms, some of which are described
- Sequential access (e.g., line scrolling, page scrolling,
tabbing access through active elements, etc.) means advancing
through rendered in well-defined steps (line by line,
screen by screen, link by link, etc.) forward and backward.
Sequential access provides context, but can be slow.
This navigation technique benefits users who cannot
scan a page for context and any user unfamiliar with the resource.
Sequential access may be based on element
type (e.g., links only), content structure (e.g., navigate
from header to header), or other criteria.
Structured navigation mechanisms allow users to move rapidly
through highly structured content such as books or
- Direct access (go to a particular link or paragraph,
search for instances of this string, etc.) is faster than
sequential access, but context is lost. Direct access benefits
users with some motor impairments and power users familiar
with a resource. Searching on text
is one important variant of direct access, but other types
of direct access are possible (e.g., navigation to a link
based on its position the page).
Selecting text or structured content with
the pointing device is another form of direct access.
User agents should allow users to configure navigation
mechanisms (e.g., to allow navigation of links only,
or links and headers, or tables and forms, etc.).
Refer also to guideline 11..
Note. For all search and navigation functions,
the user agent should follow system conventions for using
selection and focus mechanisms. For instance, the
selection should be used to identify the results of a text search,
the focus should identify
active elements during sequential navigation
of active elements, etc.
- 8.1 Allow the user to navigate viewports (including frames). [Priority 1]
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
- 8.2 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.
- 8.3 For dependent user agents only. Allow the user to navigate just among table cells of a table (notably left and right within a row and up and down within a column). [Priority 1]
Refer also to checkpoint 9.4 and checkpoint 6.2.
- 8.4 Allow the user to navigate just among all active elements. [Priority 2]
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).
- 8.5 Allow the user to search for rendered text content, including alternative text content. [Priority 2]
- 8.6 Allow the user to navigate according to the structure of the resource. [Priority 2]
- For example, allow the user to navigate familiar
elements of a document: paragraphs, tables, headers, lists,
- 8.7 Allow the user to configure structured navigation. [Priority 3]
- For example, allow the user to navigate only paragraphs,
or only headers and paragraphs, etc.
All users require clues to help them understand their "location"
when browsing. Graphical user agents provide clues such as
proportional scroll bars to indicate (roughly) one's location in a
resource. A highlighted selection or focus (either visually or
aurally) distinguishes the selected or focused content from other
content. User agent history allows users to track and undo
their browsing path. HTML 4.0 ([HTML40], section
11.2.3) allows authors to create table headers and footers (with THEAD
and TBODY) so that user agents can scroll table content while keeping
table head and foot visible on the screen.
Orientation mechanisms such as these are especially important
to users who view resources through serial means such
speech or braille (current tactile technology is limited in the amount
of information that can be displayed). Users of graphically displayed
tables can scan a table quickly to understand the position (and
related header information) of a particular cell. For users of
serial output, user agents should provide this context on demand.
Similarly, users need to know about:
- relationships between frames (e.g., how
changes in one frame affect another).
Refer also to checkpoint 10.1.
- link context. Users who browse by navigating
links only require information about links that will
allow them to decide whether to follow the link.
- form context. Users need to know when they've
provided all necessary information in a form before
For people with visual impairments, blindness, or certain types of
learning disabilities, it is important that the point of regard remain as stable as
possible. The user agent should not disturb the user's point of regard
by shifting focus to a different frame or window when an event occurs
without notifying the user of the change.
User agents must make orientation information available
in an output device-independent manner. Refer also to guideline 1.
Viewport, selection, and focus information:
- 9.1 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 10.1..
- 9.2 For dependent user agents only. Provide the user with information about the number of viewports. [Priority 2]
- Refer also to checkpoint 6.2.
- 9.3 For dependent user agents only. Allow the user to view an outline of a resource constructed from its structural elements (e.g., from header and list elements). [Priority 2]
The user should be able to control the level of detail of the
outline. Refer also to checkpoint 6.2.
- 9.4 Describe a selected element's position within larger structures (e.g., numerical or relative position in a document, table, list, etc.). [Priority 2]
For example: tenth link of fifty links;
document header 3.4; list one of two, item 4.5;
third table, three rows and four columns; current
cell in third row, fourth column; etc.
- 9.5 For a selected link, indicate whether following the link will involve a fee. [Priority 2]
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.
Refer to [MICROPAYMENT]
for information about encoding micropayment information
in markup in an interoperable manner.
- 9.6 For a selected link, provide information to help the user decide whether to follow the link. [Priority 2]
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.
- 9.7 Allow the user to configure what information about links to present. [Priority 3]
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 9.6.
- 9.8 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 supporting the appropriate style sheet
mechanisms, such as link highlighting.
- 9.9 For dependent user agents only. Provide access to header information for a selected table cell. [Priority 1]
- Refer also to checkpoint 6.2.
- 9.10 For dependent user agents only. Indicate the row and column dimensions of a selected table. [Priority 3]
Note. User agents should consider multidimensional
tables, headers and footers, and multiple header levels.
Refer also to checkpoint 6.2.
Form control information:
- 9.11 Provide information about form structure and navigation (e.g., groups of controls, control labels, navigation order, and keyboard configuration). [Priority 2]
For instance, provide information about controls with explicitly
associated labels (the "for" attribute of LABEL in HTML),
about which keys activate the form controls (the
"accesskey" attribute in HTML),
about the serial navigation order of the form controls
(the"tabindex" attribute in HTML), and about control
groups (the FIELDSET and OPTGROUP elements in HTML).
Refer also to checkpoint 1.2 and
- 9.12 Maintain consistent user agent behavior and default configurations between software releases. Consistency is less important than accessibility and adoption of system conventions. [Priority 3]
In particular, make changes conservatively to
the layout of user
interface controls, behavior of existing functionalities,
and default keyboard configuration.
Changes to content or browsing context (How many windows are
on the screen? Which is the current window?) may disorient users with
visual impairments or certain types of learning disabilities. User
agents should provide information about changes caused by scripts,
or allow users to turn off scripts entirely (refer to
User agents must ensure that notifications are available
in an output device-independent manner. Refer also to guideline 1.
- 10.1 Provide information about content and viewport changes (to users and through programming interfaces). [Priority 1]
For example, inform the users when a script causes a popup menu to appear.
- 10.2 Ensure that when the selection or focus changes, it is in the viewport after the change. [Priority 2]
- 10.3 Allow the user to selectively turn on and off notification of common types of content and viewport changes. [Priority 3]
For example, to choose to be notified (or not) that a
script has been executed, that a new window has been opened,
that a pulldown menu has been opened, that a new frame
has received focus, etc.
- 10.4 When loading a resource (e.g., document, video clip, audio clip, etc.) indicate what portion of the resource has loaded and whether loading has stalled. [Priority 3]
- 10.5 Indicate the relative position of the viewport in a resource (e.g., the percentage of the document that has been viewed, the percentage of an audio clip that has been played, 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.
- 10.6 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]
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
Web users have a wide range of
functional capabilities and so they must be able to
the user agent to meet their particular
Refer also to guideline 2. Refer also to checkpoint 9.12.
- 11.1 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
- 11.2 Allow the user to configure the graphical arrangement of user interface controls. [Priority 3]
Some people cannot use printed documentation. Vendors should
provide accessible electronic documentation for users with visual
impairments, learning disabilities, or movement impairments.
Providing alternative hardcopy formats may also benefit some users.
Since users who are not disabled are generally unaware of software
features designed specifically for accessibility, those features
should be clearly documented. This will allow users with disabilities
to learn about the software more easily.
Documentation includes all product documentation,
notably installation instructions, the help system, and all product
manuals. Refer also to guideline 2 and checkpoint 6.6.
- 12.1 Provide a version of the product documentation that conforms to the Web Content Accessibility Guidelines. [Priority 1]
Refer to [WAI-WEBCONTENT].
- 12.2 Ensure that all user agent functionalities that promote accessibility are documented. [Priority 1]
- For example,
review the documentation or help system to
ensure that it discusses the functionalities
addressed by the checkpoints of this document.
- 12.3 Describe product features known to promote accessibility in a section of the product documentation. [Priority 2]
- Applicable checkpoint
If a user agent offers a functionality, it must ensure that all users
have access to that functionality or an equivalent alternative. Thus,
if the user agent supports keyboard input, it must support accessible
keyboard input. If the user agent supports images, it must ensure
access to each image or an alternative equivalent supplied by the
author. If a user agent supports style sheets, it must implement the
accessibility features of the style sheet language. If the user agent
supports frames, it must ensure access to frame alternatives supplied
by the author.
Not all user agents support every content type, markup language
feature, input or output device interface, etc. When a content type,
feature, or device interface is not supported, checkpoints with
requirements related to it do not apply to the user agent. Thus, if
a user agent supports style sheets at all, all checkpoints related
to style sheet accessibility apply. If a user agent does not
support style sheets at all, the checkpoints do not apply.
The applicability of checkpoints related to markup language features
is measured similarly. If a user agent supports tables, it must
support the accessibility features of the language related to tables
(or images, or frames, or video, or links, etc.). The Techniques
Document includes information about the accessibility features of
W3C languages such as HTML, CSS, and SMIL.
The following summarizes criteria for applicability.
A checkpoint applies to a user agent unless:
- The checkpoint definition states explicitly that
it only applies to a different class of user agent.
- The checkpoint includes requirements about
a content type (script, image, video, sound,
applets, etc.) that the user agent does not
recognize xat all.
- The checkpoint includes requirements about a content type
that the user agent recognizes
but does not support natively.
- The checkpoint refers to the properties of an
embedded object (e.g., video or animation rate)
that may not be controlled or accessed by the user agent.
- The checkpoint includes requirements about an
unsupported markup language or other technology
(e.g., style sheets, mathematical markup language,
synchronized multimedia, metadata description language, etc.)
- The checkpoint refers to an unsupported
input or output device interface. Note that if the
interface is supported at all, it must be
- Assistive Technology
Software or hardware that has been specifically designed to assist
people with disabilities in carrying out daily activities. Assistive
technology includes wheelchairs, reading machines, devices for
grasping, etc. In the area of Web Accessibility, common
software-based assistive technologies include
dependent user agents such as
screen readers, screen
magnifiers, speech synthesizers, onscreen keyboards,
and voice input software.
Hardware assistive technologies include alternative keyboards
and pointing devices.
To set user preferences. This may be done through the user agent's
user interface, through configuration files, by scripts, etc.
- Continuous Equivalent Track
A continuous equivalent track presents an equivalent
alternative to another track (generally audio or video)
and is synchronized with that track.
Continuous equivalent tracks convey
information about spoken words and
non-spoken sounds such as sound effects.
A continuous text track presents closed captions.
Captions are generally
rendered visually by being superimposed over a video track,
which benefits people who are deaf and
hard-of-hearing, and anyone who cannot hear the audio (e.g.,
when in a crowded room).
A collated text transcript combines (collates) captions
with text descriptions of video information
(descriptions of the actions, body language, graphics, and scene
changes of the video track). These text equivalents make
presentations accessible to people who are deaf-blind and to people who
cannot play movies, animations, etc.
- One example of a non-text continuous
equivalent track is an auditory description
of the key visual elements of a presentation. The description is
either a prerecorded human voice or a synthesized voice (recorded or
generated on the fly). The auditory description is synchronized with
the audio track of the presentation, usually during natural pauses in
the audio track. Auditory descriptions include information about
actions, body language, graphics, and scene changes.
- A video track that shows sign language
is another example of a continuous equivalent track.
- Dependent User Agent
Dependent user agents rely on other user agents for input and/or
output. Dependent user agents include:
- screen magnifiers, which
are used by people with visual impairment to enlarge and
change colors on the screen to improve readability of text and images.
- screen readers, which
are used by people who are blind or with reading disabilities to
read textual information through speech or braille displays.
- alternative keyboards, which are used
by people with movement impairments to
simulate the keyboard.
- alternative pointing devices, which are used
by people with movement
impairments to simulate mouse pointing and button activations.
- Device Independence
The ability to make use of software via any input
or output device supported by the operating system.
User agents should follow system conventions and
use standard APIs for device input and output.
- Documents, Elements, and Attributes
- A document may be seen as a hierarchy of elements.
Elements are defined by a language specification (e.g., HTML 4.0 or an XML
application). Each element may have content, which generally contributes
to the document's content. Elements may also have attributes
that take values. An element's
rendered content is that which a user agent renders for the
element. This may be what lies
between the element's start and end tags, the value
of an attribute (c.f. the "alt",
"title", and "longdesc"
attributes in HTML), or external data (e.g., the
IMG element in HTML).
Rendering is not limited to graphical displays alone,
but also includes audio (speech and sound) and tactile displays
(braille and haptic displays).
Since rendered content is not always accessible, authors must specify alternative representations of content that user
agents must make available to users or software
that require it (in place of and/or in addition to the "primary"
content). Alternative representations may take a variety of forms
including alternative text, closed captions,
and auditory descriptions.
The Techniques Document ([UA-TECHNIQUES]) describes the different
mechanisms authors use to supply alternative representations of
content. Please also consult the Web Content Accessibility Guidelines
- Events and scripting
- When certain events occur (resource loading or unloading
events, mouse press or hover events, keyboard events, etc.), user
agents often perform some task (e.g., execute a script). For instance,
in most user agents, when a mouse button is released over a link, the
link is activated and the linked resource retrieved. User agents may
also execute author-defined scripts when certain events occur. The
script bound to a particular event is called an event handler. Note. The interaction of
HTML, style sheets, the Document Object Model [DOM1] and scripting is commonly referred to as
"Dynamic HTML" or DHTML. However, as there is no W3C
specification that formally defines DHTML, this document will only
refer to event handlers and scripts.
- The user focus designates an active element in a document. Which elements
are active depends on the document language and whether the
features are supported by the user agent.
In HTML documents, for example, active
elements include links, image maps, form controls, elements with a
value for the "longdesc" attribute, and elements with
associated scripts (event handlers) explicitly associated
with them (e.g., through the various "on" attributes).
An element with the focus may be activated
through any number of mechanisms, including the mouse, keyboard, an
- The effect of activation depends on the element. For instance,
when a link is activated, the user agent generally retrieves the
linked resource, which may be another Web page, program, etc. When a
form control is activated, it may change state (e.g., check boxes) or
may take user input (e.g., a text field). Activating an element with
a script assigned for that particular activation mechanism (e.g.,
mouse down event, key press event, etc.) causes the script to be
- A viewport has at most one focus. When several
viewports co-exist, each may
have a focus, but only one is active, called the current focus.
The current focus is generally presented (e.g.,
a way that makes it stand out.
Any mechanism used to emphasize selected or focused content.
Visual highlight mechanisms include dotted boxes, underlining,
and reverse video. Synthesized speech highlight mechanisms may include altering
voice pitch or volume.
- Insertion point
- The insertion point is the location where document editing takes
place. The insertion point may be set by the user (e.g., by a pointing
device or the keyboard editing keys) or through an application
programming interface (API). A viewport has at most one insertion
point. When several viewports co-exist, each may have an insertion point,
but only one is active, called the current insertion point
- The insertion point is generally rendered specially (e.g.,
on the screen, by a vertical bar or similar cursor).
- Native support
- A user agent supports a feature natively if it
does not require another piece
of software (e.g., plug-in or external program) for
support. Native support does not preclude more extensive support
for accessibility by dependent user agents, so user agents must
still make information available through programming interfaces.
- Natural Language
Spoken, written, or signed human languages such as French,
Japanese, American Sign Language, and braille.
The natural language of content may be indicated in
markup (e.g., by the "lang" attribute in HTML ([HTML40], section 8.1) or
by HTTP headers.
- Properties, Values, and Defaults
- A user agent renders a document by applying formatting algorithms and
style information to the document's elements. Formatting depends on a
number of factors, including where the document is rendered:
on screen, paper, through speakers, a braille device, a mobile
device, etc. Style information
(e.g., fonts, colors, voice inflection, etc.)
may come from the elements themselves
(e.g., certain style attributes in HTML), from style sheets, or
from user agent settings. For the purposes of these guidelines, each
formatting or style option is governed by a property
and each property may take one value from a set of legal
values. (The term "property"
in this document has the meaning ascribed in the
CSS2 Recommendation [CSS2].)
A reference to "styles" in this document means a set
of style-related properties.
- The value given to a property by a user agent when it is started up is
called the property's default value. User agents may allow users to change default
values through a variety of mechanisms (e.g., the user interface, style
sheets, initialization files, etc.).
- Once the user agent is running, the value of a property for a given
document or part of a document may be changed from the default value. The
value of the property at a given moment is called its
Note that changes in the current value of a property do not change its
- Current values may come from documents, style sheets, scripts, or the
user interface. Values that come from documents, their associated style
sheets, or via a server are called author styles. Values that come from user interface settings,
user style sheets, or other user interactions are called
- A user agent is said to recognize
markup, content types, or rendering effects
when it can identify (through built-in
mechanisms, DTDs, style sheets,
headers, etc) the information.
For instance, HTML 3.2 user agents may
not recognize the new elements or attributes
of HTML 4.0. Similarly, a user agent may
recognize blinking content
specified by elements or attributes,
but may not recognize that an applet is blinking.
The Techniques Document ([UA-TECHNIQUES])
discusses some content that affects accessibility
and should be recognized as such.
- The user selection generally specifies a range of content (text,
images, etc.) in a document. The range may be restricted to the
content of a single element or may span several elements. The
selection may be used for a variety of purposes: for cut and paste
operations, to designate a specific element in a document, to identify
what a screen reader should read, etc.
- The user selection may be set by the user (e.g., by a pointing
device or the keyboard) or through an application programming
interface (API). A viewport has at most one user selection. When several
viewports co-exist, each may have a user selection, but only one is
active, called the current user selection.
- The user selection is usually presented in a
way the stands out (e.g., highlighted). On the screen, the
selection may be highlighted using colors, fonts, graphics, or other
mechanisms. Highlighted text is often used by dependent user agents to indicate through
speech or braille output what the user wants to read. Most screen
readers are sensitive to highlight colors. Dependent user agents may
provide alternative presentation of the selection through speech,
enlargement, or refreshable braille display.
- Text transcript
A text transcript
is a text equivalent of audio information that includes spoken
words and non-spoken sounds such as sound effects.
Refer also to continuous equivalent track.
- User Agent
A user agent is an application that retrieves and renders Web
resources, including text, graphics, sounds, video, images, and other
objects. An user agent may require additional software to handle some
types of content. For instance, a browser may run a separate program
or plug-in to render sound or video. The additional software is also
considered a user agent.
User agents include graphical desktop browsers, multimedia
players, text browsers, voice browsers, and dependent user agents such as screen
readers, screen magnifiers, speech synthesizers, onscreen keyboards,
and voice input software.
- Views, Viewports, and Point of Regard
- User agents may handle different types of source information:
documents, sound objects, video objects, etc. The user perceives the
information through a viewport, which may be a window, frame, a
piece of paper, a panner, a speaker, a virtual magnifying glass, etc. A
viewport may contain another viewport (e.g., nested frames, plug-ins,
- User agents may render the same source information in a variety of
ways; each rendering is called a view. For instance, a user agent may
allow users to view an entire document or just a list of
the document's headers. These are two different views
of the document.
- The view is how source information is
rendered and the viewport is where it is rendered. Both the
current focus and the current user selection must be in the same
viewport, called the current viewport. The current viewport is
generally highlighted when several viewports co-exist.
- Generally, viewports give users access to all rendered information,
though not always at once. For example, a video player shows a certain
number of frames per second, but allows the user to rewind and fast
forward. A graphical browser viewport generally features scrollbars or
some other paging mechanism that allows the user to bring the rendered
content into the viewport.
- The content currently available in the viewport is called the
user's point of regard. The point of regard may be a two dimensional
area (e.g., for graphical rendering) or a single point (e.g., for
aural rendering or voice browsing).
User agents should not change the point of regard
unexpectedly as this can disorient users.
Many thanks to the following people who have contributed
through review and comment: Paul Adelson, James Allan, Denis
Anson, Kitch Barnicle, Harvey Bingham, Olivier Borius, Judy
Brewer, Bryan Campbell, Kevin Carey, Wendy Chisholm, David Clark,
Chetz Colwell, Wilson Craig, Nir Dagan, Daniel Dardailler,
B. K. Delong, Neal Ewers, Geoff Freed, John Gardner, Al Gilman,
Larry Goldberg, Glen Gordon,
John Grotting, Markku Hakkinen, Earle Harrison,
Chris Hasser, Kathy Hewitt, Philipp Hoschka, Masayasu Ishikawa,
Phill Jenkins, Jan Kärrman (for help with html2ps),
Leonard Kasday, George Kerscher, Marja-Riitta
Koivunen, Josh Krieger, Catherine Laws, Greg Lowney, Scott
Luebking, William Loughborough, Napoleon Maou, Charles
McCathieNevile, Masafumi Nakane, Mark Novak, Charles Oppermann,
Mike Paciello, David Pawson, Michael Pederson, Helen Petrie, David
Poehlman, Michael Pieper, Jan Richards, Hans Riesebos, Joe Roeder,
Lakespur L. Roca, Gregory Rosmaita, Lloyd Rutledge, Liam Quinn,
T.V. Raman, Robert Savellis, Rich Schwerdtfeger, Constantine
Stephanidis, Jim Thatcher, Jutta Treviranus, Claus Thogersen,
Steve Tyler, Gregg Vanderheiden, Jaap van Lelieveld, Jon S. von
Tetzchner, Willie Walker, Ben Weiss, Evan Wies, Chris Wilson, Henk
Wittingen, and Tom Wlodkowski,
For the latest version of any W3C specification, please consult the
list of W3C Technical Reports.
"CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds.,
17 December 1996, revised 11 January 1999. This CSS1 Recommendation
"CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C. Lilley,
and I. Jacobs, eds., 12 May 1998. This CSS2 Recommendation is
"Accessibility Features of CSS", I. Jacobs, J. Brewer,
The latest version of this W3C Note is available at
"Document Object Model (DOM) Level 1 Specification",
V. Apparao, S. Byrne, M. Champion, S. Isaacs, I. Jacobs, A. Le Hors, G. Nicol,
J. Robie, R. Sutor, C. Wilson, and L. Wood, eds. The 1 October
1998 DOM Level 1 Recommendation is
"Document Object Model (DOM) Level 2 Specification",
L. Wood, A. Le Hors, V. Apparao,
L. Cable, M. Champion, J. Kesselman,
P. Le Hégaret, T. Pixley, J. Robie,
P. Sharpe, C. Wilson, eds. The DOM2 specification is
a Working Draft at the time of publication.
"HTML 4.0 Recommendation", D. Raggett, A. Le Hors, and I.
Jacobs, eds. The 24 April 1998 HTML 4.0 Recommendation is
"HTML 3.2 Recommendation", D. Raggett, ed. The HTML 3.2
Recommendation is http://www.w3.org/TR/REC-html32
"Mathematical Markup Language", P. Ion and R. Miner, eds. The
7 April 1998 MathML 1.0 Recommendation is
"Common Markup for micropayment per-fee-links",
T. Michel, ed. The latest version of this
W3C Working Draft is available at
"Key words for use in RFCs to Indicate Requirement Levels",
S. Bradner, March 1997.
"Synchronized Multimedia Integration Language (SMIL) 1.0
Specification", P. Hoschka, editor.
The 15 June 1998 SMIL 1.0 Recommendation is
"Accessibility Features of SMIL", M-R. Koivunen, I. Jacobs.
The latest version of this W3C Note is available at
"Techniques for User Agent Accessibility Guidelines 1.0", J. Gunderson, I. Jacobs, eds.
This document explains how to implement the checkpoints defined
in "User Agent Accessibility Guidelines 1.0". The latest draft of the techniques is
available at http://www.w3.org/WAI/UA/WAI-USERAGENT-TECHS/
"Authoring Tool Accessibility Guidelines", J. Treviranus,
J. Richards, I. Jacobs, C. McCathieNevile, eds.
The latest Working Draft of these guidelines for designing
accessible authoring tools is available at
"Web Content Accessibility Guidelines 1.0", W. Chisholm,
G. Vanderheiden, and I. Jacobs, eds.
The 5 May 1999 Recommendation is
"Techniques for Web Content Accessibility Guidelines 1.0", W. Chisholm,
G. Vanderheiden, and I. Jacobs, eds.
The latest version of this document is available at
"Extensible Markup Language (XML) 1.0.", T. Bray, J. Paoli, C.M.
Sperberg-McQueen, eds. The 10 February 1998
XML 1.0 Recommendation is