This document provides guidelines to user agent manufacturers for
making their products more accessible to people with disabilities and
for increasing usability for all users. This document emphasizes the
accessibility of interoperability between two important classes of
user agents - graphical desktop browsers and dependent assistive
technologies (screen readers, screen magnifiers, braille
displays, and voice
input software). However, it is meant to be applicable to user
agents in general, including text and voice browsers, multimedia
players, and plug-ins.
This document includes an appendix that organizes all of the checkpoints by topic and priority.
The checkpoints in the appendix link to their definitions in the
current document. The topics identified in the appendix include
user interface, keyboard support,
images, multimedia, tables, frames, forms, and scripts.
This appendix is available both as a tabular summary and as a
simple list of
checkpoints.
A separate document, entitled "Techniques for User Agent Accessibility Guidelines 1.0" ([UA-TECHNIQUES]), explains how to implement
the checkpoints defined in the current document. The Techniques
Document discusses each checkpoint in more detail and provides
examples using the
Hypertext Markup Language (HTML),
Cascading Style Sheets (CSS),
Synchronized Multimedia Integration Language
(SMIL),
and the Mathematical Markup Language (MathML). The Techniques Document has been designed to
track changes in technology and is expected to be updated
more frequently than the current document.
Note. Some browsers or multimedia tools
may not support some of the features described in the guidelines.
In particular, new features of HTML 4.0 or CSS 1 or CSS 2 may not be
supported.
"User Agent Accessibility Guidelines 1.0" is part of a series of accessibility guidelines
published by the Web Accessibility
Initiative. The series also includes Web Content Accessibility
Guidelines ([WAI-WEBCONTENT]) and
Authoring Tool Accessibility Guidelines ([WAI-AUTOOLS]).
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.
Please send comments about this document to the public mailing list:
w3c-wai-ua@w3.org.
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 current Working Group
members is
available.
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 using
documents 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 the document is written.
- 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.).
The guidelines in this document are designed to help developers
understand and thereby reduce accessibility barriers that impede
access to the Web. The associated Techniques Document
([UA-TECHNIQUES])
provides practical solutions based on
existing and upcoming technologies. Though developers may believe
that implementing accessibility features in their products is
difficult or of limited use, considering accessibility during the
design phase of a product leads to more flexible, manageable, and
extensible software.
These guidelines include information relevant to a wide class of
user agents: graphical desktop browsers, screen readers, speech
synthesizers, multimedia players, text browsers, voice browsers,
plug-ins, etc., with a particular focus on two classes of user
agents:
- Graphical desktop browsers
- Dependent user
agents, which rely on of 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.
The guidelines emphasize interoperability between these two
classes of user agents.
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 functionality offered by the user
agent through its user interface. This includes the functionalities
built into the tool as well as those offered via the document: links,
form controls, applets, and other interactive elements.
The general topic of user interface accessibility for computer
software exceeds the scope of this document. The
Techniques Document contains some pointers to software
accessibility guidelines for
The guidelines do discuss 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.
Through the user interface, users must have access to document
content, including alternative content
(e.g., "alt" attribute text in HTML). To ensure access to content,
users must have final control of the style (colors, fonts, speech
rate, speech volume, etc.) and format of a document.
User agents may facilitate access to content by providing a
convenient user interface (e.g., scrolled viewport) and navigation
mechanisms (e.g., allowing users to tab to
active elements of a document).
Orientation - the sense of where one is within a document or series
of documents - is fundamental to a successful Web experience. Visual
mechanisms that promote orientation include:
- proportional scroll
bars, which indicate how much of the document has been read
- frames, which suggest content relationships
- graphical site maps, which describe page organization
Some users cannot use visual orientation clues and require other
mechanisms to remain oriented:
- Contextual information about document elements. For instance,
users with blindness who navigate by surfing only the links
of a document benefit from knowing how many links the document
contains or the number of the current link. Numerical position
information, in conjunction with a navigation mechanism that allows
users to jump directly to a given link, can greatly facilitate
browsing, especially for documents with many links.
- Contextual information about the
document or views (e.g., how many views,
whether the document has finished loading, whether
the user can begin to browse, etc.)
- Summary information about specific elements (e.g.,
the dimensions of a table).
- Alerts when events occur during browsing (e.g.,
a window opens, a script is executed, etc.).
The user agent should also minimize the chances the
user will become disoriented by allowing the user to control when
windows are spawned, warning the user when events occur, avoiding
sudden movements of the viewport, etc.
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 user agents, which must make information
available to assistive technologies. Even when a user agent
implements a feature natively, it should make information available to
other software. Scripting tools and automated test engines also
benefit from having access to user agent information through standard
interfaces.
Implementing interoperable specifications (such as those produced by
W3C) promotes accessibility for several reasons:
- W3C technologies 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.
This document includes fourteen guidelines, or general principles of
accessible design. 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 in typical content
development scenarios. 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 section of the
Techniques Document ([UA-TECHNIQUES]) where
implementations and examples of the checkpoint are discussed.
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
this document:
- 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 implemented by user
agents as a native
feature or through compatibility with assistive
technology, 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 implemented by user agents
as a native feature or through compatibility with assistive
technology, 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 implemented by user
agents as a native feature or through compatibility with assistive
technology, 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]).
To promote interoperability between desktop graphical user agents and dependent user agents, conformance to
this document is expressed in terms of these two types of software.
In order to conform as a desktop graphical user agent,
the user agent must do all of the following:
- Satisfy all the checkpoints (for a chosen
conformance level)
that apply to
desktop graphical user agents, and
- Satisfy each checkpoint
natively
unless the checkpoint explicitly indicates
that it may be satisfied through communication with other software.
Even for those checkpoints that must be satisfied natively, desktop
graphical user agents should make information available to other
software through standard interfaces (e.g., specialized dependent
user agents may provide a better solution to a problem
than a desktop user agent).
In order to conform as a dependent user agent, the user agent must
do all of the following:
- Satisfy all the checkpoints (for a chosen
conformance level)
that apply to
dependent user agents, and
- Satisfy each checkpoint
natively
unless the checkpoint explicitly indicates
that it may be satisfied through communication with other software.
This section defines three levels of conformance to this
document.
- 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 to 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-19990716
- The conformance level satisfied: "A", "Double-A", or "Triple-A".
- The class of user agent covered by the claim: desktop graphical
user agent or dependent user agent.
Example of Form 1:
This product conforms as a desktop graphical
user agent to W3C's "User Agent Accessibility Guidelines 1.0",
available at http://www.w3.org/WAI/UA/WAI-USERAGENT-19990716, level Double-A.
or:
This screen reader conforms as a dependent
user agent to W3C's "User Agent Accessibility Guidelines 1.0",
available at http://www.w3.org/WAI/UA/WAI-USERAGENT-19990716, 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.
Input devices include pointing devices,
keyboards, braille devices, head wands, microphones, touch screens, and
others. Output devices may include monitors, speech synthesizers,
braille devices, and printers.
Please note that "device-independent support" does not mean that
user agents must support every input or output device. User agents
should offer redundant input and output mechanisms for those devices
that are supported. For example, if a user agent supports keyboard
and mouse input, users should be able to interact with all features
using either the keyboard or the mouse.
- 1.1 Ensure that all functionalities offered by the user agent interface are available through all supported input devices. [Priority 1]
- Techniques for checkpoint 1.1
- 1.2 Ensure that the user can interact with all active elements of a document in a device-independent manner. [Priority 1]
- Techniques for checkpoint 1.2
- 1.3 Ensure that the user can install the user agent software in a device-independent manner. [Priority 1]
- Techniques for checkpoint 1.3
- 1.4 Ensure that the user can configure the user agent in a device-independent manner. [Priority 1]
- Techniques for checkpoint 1.4
- 1.5 Ensure that the user can access user agent documentation in a device-independent manner. [Priority 1]
- Techniques for checkpoint 1.5
- 1.6 Ensure that all messages to the user (e.g., warnings, errors, etc.) are available in an output device-independent manner using any supported output devices. [Priority 1]
- Techniques for checkpoint 1.6
Although keyboard access may seem to contradict the previous
guideline on device-independence, ensuring keyboard access to
user agent functionality 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 through software. This guideline
is important for ensuring compatibility between desktop
graphical user agents and dependent assistive technologies.
Checkpoints in this section do not apply to user agents (e.g.,
kiosks) that do not natively support keyboard input.
One area where configurability is important involves keyboard
access to user agent functionality. 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.
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 9.25.
- 2.1 By default and without additional customization, ensure that all functionalities offered by the user agent are accessible using the keyboard. [Priority 1]
- Note. This checkpoint intends
to ensure compatibility with assistive technologies that
rely on keyboard input. Functionalities include
being able to show, hide, resize and move windows
or panes created by the user agent.
- Techniques for checkpoint 2.1
- 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 3.
- Techniques for checkpoint 2.2
- 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 3.
- Techniques for checkpoint 2.3
- 2.4 Allow the user to configure the keystrokes used to activate user agent functionalities. Wherever possible, allow single key activation of functions. [Priority 2]
- Techniques for checkpoint 2.4
- 2.5 Allow the user to turn on and off author-specified keyboard configurations. [Priority 2]
- Techniques for checkpoint 2.5
- 2.6 Indicate the keyboard access method to activate a user agent function using platform conventions. [Priority 2]
- Techniques for checkpoint 2.6
- 2.7 Avoid default keyboard configurations that interfere with system conventions. [Priority 2]
-
For example, the default configuration should not include
"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 12.
- Techniques for checkpoint 2.7
- 2.8 Provide a default keyboard configuration for frequently performed operations. [Priority 3]
- Techniques for checkpoint 2.8
Users who may not be able to access print material, including
individuals with visual impairments, learning disabilities, or
movement impairments, may be able to use accessible electronic
documentation or documents in alternative hardcopy formats.
Documentation includes
all product documentation, notably installation
instructions, the help system, and all product manuals.
Refer also to guideline 2 and checkpoint 12.6.
- 3.1 Ensure that all product documentation conforms to the Web Content Accessibility Guidelines. [Priority 1]
-
Refer to [WAI-WEBCONTENT].
- Techniques for checkpoint 3.1
- 3.2 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.
- Techniques for checkpoint 3.2
- 3.3 Describe product features known to promote accessibility in a section of the product documentation. [Priority 2]
- Techniques for checkpoint 3.3
Refer also to guideline 2. Refer also to checkpoint 9.25.
- 4.1 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
default settings).
- Techniques for checkpoint 4.1
- 4.2 Allow the user to configure the visual arrangement of user interface controls. [Priority 3]
- Techniques for checkpoint 4.2
User agents are only expected to provide
this control for content that it recognizes. Refer also to guideline 6.
- 5.1 Allow the user to turn on and off rendering of images. [Priority 1]
- Techniques for checkpoint 5.1
- 5.2 Allow the user to turn on and off rendering of background images. [Priority 1]
- Techniques for checkpoint 5.2
- 5.3 Allow the user to turn on and off rendering of video. [Priority 1]
- Techniques for checkpoint 5.3
- 5.4 Allow the user to turn on and off rendering of sound. [Priority 1]
- Techniques for checkpoint 5.4
- 5.5 Allow the user to turn on and off rendering of captions. [Priority 1]
- Techniques for checkpoint 5.5
- 5.6 Allow the user to turn on and off animated or blinking text. [Priority 1]
- Note. This is particularly important
for users with screen readers.
- Techniques for checkpoint 5.6
- 5.7 Allow the user to turn on and off animations and blinking images. [Priority 1]
- Techniques for checkpoint 5.7
- 5.8 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.
- Techniques for checkpoint 5.8
- 5.9 Allow the user to turn on and off support for user style sheets. [Priority 1]
- Techniques for checkpoint 5.9
- 5.10 Allow the user to turn on and off support for author style sheets. [Priority 1]
- Techniques for checkpoint 5.10
- 5.11 Allow the user to turn on and off support for spawned windows. [Priority 1]
- Techniques for checkpoint 5.11
- 5.12 Allow the user to turn on and off rendering of frames. [Priority 2]
- Techniques for checkpoint 5.12
- 5.13 Allow the user to turn on and off author-specified page forwards that occur after a time delay and without user intervention. [Priority 3]
- Techniques for checkpoint 5.13
- 5.14 Allow the user to turn on and off automatic page refresh. [Priority 3]
- Techniques for checkpoint 5.14
In order to access a document, some users may require that it be
rendered in a manner other than what the author intended. Users who
are color-deficient may not be able to perceive certain color
combinations. Users with low vision may require large fonts. Users
who are blind may require audio or tactile rendering. Users who are
deaf may require captions for audio files.
User agents must therefore allow the user to control:
- The document's style (e.g., fonts, colors, aural
parameters, etc.)
- The document's formatting: whether the document is presented
textually, graphically, linearly, aurally, for tactile
use, or some combination of these.
- The document's content. This means whether primary content
or alternative representations of content or both are rendered.
- The user interface. Since authors may make changes to the
user interface through scripting (e.g., by spawning new
windows, causing dialog boxes to appear, etc.), users must
be able to override changes that make the user agent or
document inaccessible.
Otherwise, users who are blind, have visual impairments, some types
of learning disabilities, or any user who cannot or has chosen not to
view the primary representation of information will not know content
of the information on the page.
The following checkpoints state which styles the user must be able
to control. The checkpoints also require user agents to allow users to
override author styles and user agent defaults. The checkpoints
apply to alternative representations of
content as well as primary content.
Checkpoints for fonts and colors:
- 6.1 Allow the user to control font family. [Priority 1]
- Techniques for checkpoint 6.1
- 6.2 Allow the user to control font size. [Priority 1]
- Techniques for checkpoint 6.2
- 6.3 Allow the user to control foreground color. [Priority 1]
- Techniques for checkpoint 6.3
- 6.4 Allow the user to control background color. [Priority 1]
- Techniques for checkpoint 6.4
- 6.5 Allow the user to control selection highlighting (e.g., foreground and background color). [Priority 1]
- Techniques for checkpoint 6.5
- 6.6 Allow the user to control focus highlighting (e.g., foreground and background color). [Priority 1]
- Techniques for checkpoint 6.6
See also checkpoints checkpoint 7.12 and
checkpoint 7.13.
Checkpoints for applets and animations:
- 6.7 Allow the user to control animation rate. [Priority 2]
- Techniques for checkpoint 6.7
Checkpoints for video.
- 6.8 Allow the user to control video frame rates. [Priority 1]
- Techniques for checkpoint 6.8
- 6.9 Allow the user to control the position of captions. [Priority 1]
- Techniques for checkpoint 6.9
- 6.10 Allow the user to start, stop, pause, and rewind video. [Priority 2]
- Techniques for checkpoint 6.10
Checkpoints for audio:
- 6.11 Allow the user to control audio playback rate. [Priority 1]
- Techniques for checkpoint 6.11
- 6.12 Allow the user to control audio volume. [Priority 2]
- Techniques for checkpoint 6.12
- 6.13 Allow the user to start, stop, pause, and rewind audio. [Priority 2]
- Techniques for checkpoint 6.13
Checkpoints for speech:
- 6.14 Allow the user to control speech playback rate. [Priority 1]
- Techniques for checkpoint 6.14
- 6.15 Allow the user to control speech volume, pitch, gender and other articulation characteristics. [Priority 2]
- Techniques for checkpoint 6.15
Checkpoints for changes to the user interface:
- 6.16 When new windows or user interface components are spawned, allow the user to control window size and position. [Priority 2]
- Techniques for checkpoint 6.16
Otherwise, some users cannot perceive the primary content due to a
disability or a technological limitation (e.g., browser configured not
to display images).
General checkpoints:
- 7.1 Ensure that the user has access to document 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.
- Techniques for checkpoint 7.1
- 7.2 For dependent user agents. 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.
- Techniques for checkpoint 7.2
- 7.3 For dependent user agents. Support marked-up changes in natural language of content. For unsupported languages, notify the user of the change. [Priority 2]
- Techniques for checkpoint 7.3
- 7.4 When no alternative text representation has been specified, indicate what type of object is present. [Priority 2]
- Techniques for checkpoint 7.4
- 7.5 When alternative text has been specified explicitly as empty (i.e., an empty string), render nothing. [Priority 3]
- Techniques for checkpoint 7.5
Checkpoints for audio:
- 7.6 If a technology allows for more than one caption or description track for audio, allow the user to choose from among tracks. [Priority 1]
- Techniques for checkpoint 7.6
- 7.7 Allow the user to specify that captions for audio be rendered at the same time as the audio. [Priority 1]
- Techniques for checkpoint 7.7
Checkpoints for video:
- 7.8 If a technology allows for more than one caption or description track (e.g., text, video of sign language, etc.) for video, allow the user to choose from among tracks. [Priority 1]
- Techniques for checkpoint 7.8
- 7.9 If a technology allows for more than one audio track for video, allow the user to choose from among tracks. [Priority 1]
- Techniques for checkpoint 7.9
- 7.10 Allow the user to specify that text descriptions of video be rendered at the same time as the video. [Priority 1]
- Techniques for checkpoint 7.10
- 7.11 Allow the user to specify that auditory descriptions of video be rendered at the same time as the video. [Priority 1]
- Techniques for checkpoint 7.11
Checkpoints for links:
- 7.12 Provide a mechanism (e.g., through style sheets) to distinguish visited links from unvisited links. [Priority 3]
- Note. Using color as the only distinguishing
factor does not suffice since color may not be perceivable
by all users or rendered by all devices.
- Techniques for checkpoint 7.12
- 7.13 Allow the user to specify (e.g., through style sheets) that images used in links must have borders. [Priority 3]
- Techniques for checkpoint 7.13
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 views (notably those with frame viewports). [Priority 1]
-
Note. Navigating into a view makes it the
current view.
- Techniques for checkpoint 8.1
- 8.2 Keep track of the user's point of regard in each view and restore it when the user returns to the view. [Priority 1]
- Techniques for checkpoint 8.2
- 8.3 For dependent user agents. Allow the user to navigate among table cells of a table (notably left and right within a row and up and down within a column). [Priority 1]
- Techniques for checkpoint 8.3
- 8.4 Allow the user to navigate among all active elements in the document. [Priority 2]
-
Navigation mechanisms may range from sequential (e.g.,
tabbing navigation) 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).
- Techniques for checkpoint 8.4
- 8.5 Allow the user to search for rendered text content, including alternative text content. [Priority 2]
- Techniques for checkpoint 8.5
- 8.6 Allow the user to navigate the document structure. [Priority 2]
- For example, allow the user to navigate familiar
elements of a document: paragraphs, tables, headers, lists,
etc.
- Techniques for checkpoint 8.6
- 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.
- Techniques for checkpoint 8.7
Document information:
Users that are viewing documents through linear channels of
perception like speech (since speech is temporal in nature) and
tactile displays (current tactile technology is limited in the amount
of information that can be displayed) have difficulty maintaining a
sense of their relative position in a document. The meaning of
"relative position" depends on the situation. It may mean
the distance from the beginning of the document to the point of regard (how much of the
document has been read), it may mean the cell currently being examined
in a table, or the position of the current document in a set of
documents.
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.
View, selection, and focus information:
- 9.1 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current view. [Priority 1]
- Techniques for checkpoint 9.1
- 9.2 Provide a mechanism for highlighting and identifying (through a standard interface where available) the user selection. [Priority 1]
- Techniques for checkpoint 9.2
- 9.3 Provide a mechanism for highlighting and identifying (through a standard interface where available) the current focus. [Priority 1]
- Techniques for checkpoint 9.3
- 9.4 For dependent user agents. Provide the user with information about the number of viewports. [Priority 2]
- Techniques for checkpoint 9.4
- 9.5 Ensure that when the selection changes, it is in the viewport after the change. [Priority 2]
- Techniques for checkpoint 9.5
- 9.6 Ensure that when the focus changes, it is in the viewport after the change. [Priority 2]
- Techniques for checkpoint 9.6
- 9.7 Identify a frame selected by the user. [Priority 2]
- Techniques for checkpoint 9.7
Document information:
- 9.8 For dependent user agents. Allow the user to view a document outline constructed from its structural elements (e.g., from header and list elements). [Priority 2]
- Techniques for checkpoint 9.8
- 9.9 Make available the primary language of a document's content. [Priority 3]
- For example, use HTTP header information or
language attribute information from the document root.
- Techniques for checkpoint 9.9
- 9.10 Make available the number of links (to distinct targets) in a document. [Priority 3]
- Techniques for checkpoint 9.10
- 9.11 Make available the number of visited links (to distinct targets) in a document. [Priority 3]
- Techniques for checkpoint 9.11
- 9.12 Make available the number of tables in a document. [Priority 3]
- Techniques for checkpoint 9.12
- 9.13 Make available the number of form controls in a document. [Priority 3]
- Techniques for checkpoint 9.13
- 9.14 Make available what portion of the document has loaded. [Priority 3]
- Techniques for checkpoint 9.14
Link information:
- 9.15 Identify a link selected by the user. [Priority 3]
- For instance, the link's
integer position in the document.
- Techniques for checkpoint 9.15
- 9.16 Make available whether a chosen link (target) has already been visited. [Priority 3]
- Techniques for checkpoint 9.16
- 9.17 Make available whether a chosen link (target) is local to the document. [Priority 3]
- Techniques for checkpoint 9.17
- 9.18 Make available whether following a link will involve a fee. [Priority 3]
- Techniques for checkpoint 9.18
Table information:
- 9.19 Identify a table selected by the user. [Priority 3]
- For instance, the table's
integer position in the document.
- Techniques for checkpoint 9.19
- 9.20 Make available the dimensions of a chosen table. [Priority 3]
- Techniques for checkpoint 9.20
Table cell information:
- 9.21 For dependent user agents. Provide access to header information for a table cell selected by the user. [Priority 1]
- Techniques for checkpoint 9.21
- 9.22 Identify the table containing a table cell selected by the user. [Priority 3]
- Techniques for checkpoint 9.22
- 9.23 Make available the coordinates in the current table of a selected table cell. [Priority 3]
- Techniques for checkpoint 9.23
Form control information:
- 9.24 Provide the user with access to any label explicitly associated with a form control. [Priority 2]
- Techniques for checkpoint 9.24
Consistency:
- 9.25 Maintain consistent user agent behavior and default configurations between software releases. Consistency is less important than accessibility and adoption of system conventions. [Priority 3]
-
Changes to layout of user
interface controls, behavior of existing functionalities,
default keyboard configuration, and other user agent
features should not be arbitrary.
- Techniques for checkpoint 9.25
To avoid confusion that the effects of scripts may cause, users
should be notified when scripts are executed (or be able to disable scripts entirely). This is
also important for security reasons; users should be able to decide
whether to allow scripts to execute on their machines.
- 10.1 Provide information about document changes (to the user and through programming interfaces). [Priority 1]
- Techniques for checkpoint 10.1
- 10.2 Allow the user to configure the user agent for notification of certain types of document changes only. [Priority 3]
- Techniques for checkpoint 10.2
- 10.3 Notify the user when enough of the document has loaded in order to begin to browse. [Priority 3]
- Techniques for checkpoint 10.3
- 10.4 Notify the user when document loading has stalled. [Priority 3]
- Techniques for checkpoint 10.4
- 10.5 Allow the user to request to be prompted before a form is submitted. [Priority 3]
- Techniques for checkpoint 10.5
The current guidelines recommend support for
W3C technologies (e.g., HTML, CSS, MathML, SMIL, etc.) for several reasons:
- W3C technologies 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.
- 11.1 Implement the accessibility features defined for supported technologies. [Priority 1]
- Note. The
Techniques Document ([UA-TECHNIQUES])
discusses accessibility features of W3C technologies.
- Techniques for checkpoint 11.1
- 11.2 Support appropriate W3C Recommendations. [Priority 2]
- For instance, for document markup,
support HTML and XML; for style sheets, support CSS; for
mathematics, support MathML; for multimedia, support SMIL, etc.
- Techniques for checkpoint 11.2
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
settings.
- 12.1 Use and provide accessible interfaces to other technologies. [Priority 1]
- To promote interoperability, open standards and W3C
specifications should be used wherever possible.
- Techniques for checkpoint 12.1
- 12.2 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]
- Techniques for checkpoint 12.2
- 12.3 Notify dependent user agents of changes to the document and user interface controls (including selection and focus) by using operating system and development language accessibility resources and conventions. [Priority 1]
- Techniques for checkpoint 12.3
- 12.4 For desktop graphical browsers. Comply with W3C Document Object Model specifications and export interfaces defined by those specifications. [Priority 1]
- For example, refer to [DOM, Level 1]. 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 for checkpoint 12.4
- 12.5 For desktop graphical browsers. Provide programmatic exchange of information in a timely manner. [Priority 2]
- This is important
for synchronous alternative renderings and simulation of events.
- Techniques for checkpoint 12.5
- 12.6 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.
- Techniques for checkpoint 12.6
- Applicable checkpoint
- 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 addresses a content type
(script, image, video, sound, applets, etc.) that the user agent
does not recognize.
- The checkpoint refers to 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.
- 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 visual 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, text 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
([WAI-WEBCONTENT]).
- Events and scripting
- When certain events occur (document 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.
- Focus
- 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, form controls, elements with a
value for the "longdesc" attribute, and elements with
associated scripts (event handlers). An element with the focus may be activated
through any number of mechanisms, including the mouse, keyboard, an
API, etc.
- 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
executed.
- A view has at most one focus. When several views co-exist, each may
have a focus, but only one is active, called the current
focus.
The current focus is generally presented (e.g., highlighted) in
a way that makes it stand out.
- 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 view has at most one insertion
point. When several views 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 assistive technologies, so user agents must
still make information available through programming interfaces.
- 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.)
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
current value.
Note that changes in the current value of a property do not change its
default value.
- 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
user
styles.
- Recognize
- 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 visually 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.
- Selection
- 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 view has at most one user selection. When several
views 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.
- Both the current focus and the current user selection must be in
the same view, called the current view. The current view is
generally highlighted when several views co-exist.
- 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 speaker, a virtual magnifying glass, etc. A
viewport may contain another viewport (e.g., nested frames, plug-ins,
etc.).
- 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 a document in one window and a generated list of
headers for the document in another.
- The view is how source information is rendered and the
viewport is where it is rendered.
- 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 visual 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, 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, Greg 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,
- [CSS1]
- "CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds. The
CSS1 Recommendation is:
http://www.w3.org/TR/1999/REC-CSS1-19990111.
- [CSS2]
- "CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C. Lilley,
and I. Jacobs, eds. The CSS2 Recommendation is:
http://www.w3.org/TR/1998/REC-CSS2-19980512.
- [DOM1]
- "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 DOM Level 1
Recommendation is:
http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001.
- [HTML40]
- "HTML 4.0 Recommendation", D. Raggett, A. Le Hors, and I.
Jacobs, eds. The HTML 4.0 Recommendation is:
http://www.w3.org/TR/1998/REC-html40-19980424.
- [HTML32]
- "HTML 3.2 Recommendation", D. Raggett, ed. The HTML 3.2
Recommendation is:
http://www.w3.org/TR/REC-html32.
- [MATHML]
- "Mathematical Markup Language", P. Ion and R. Miner, eds. The MathML 1.0
Recommendation is:
http://www.w3.org/TR/1998/REC-MathML-19980407.
- [RFC2119]
- "Key words for use in RFCs to Indicate Requirement Levels",
S. Bradner, March 1997.
Available at
http://www.ietf.org/rfc/rfc2119.txt
- [SMIL]
- "Synchronized Multimedia Integration Language (SMIL) 1.0
Specification", P. Hoschka, editor. The SMIL 1.0 Recommendation is:
http://www.w3.org/TR/1998/REC-smil-19980615
- [UA-TECHNIQUES]
- "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/
- [WAI-AUTOOLS]
- "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:
http://www.w3.org/TR/WD-WAI-AUTOOLS/
- [WAI-WEBCONTENT]
- "Web Content Accessibility Guidelines", W. Chisholm,
G. Vanderheiden, and I. Jacobs, eds., 5 May 1999.
This W3C Recommendation is
http://www.w3.org/TR/1999/WAI-WEBCONTENT-19990505.
- [XML]
- "Extensible Markup Language (XML) 1.0.", T. Bray, J. Paoli, C.M.
Sperberg-McQueen, eds. The XML 1.0 Recommendation is:
http://www.w3.org/TR/1998/REC-xml-19980210
