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, 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 is part of a series of accessibility documents published
by the W3C Web Accessibility Initiative.
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 process
some types of information easily or at all.
- 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.)
- They may have difficulty seeing, reading, or comprehending
text.
- They may have difficulty seeing, reading, or comprehending
images.
- They may not have or be able to use a keyboard or mouse.
- They may have an early version of a browser, a different
browser entirely, a voice browser, or a
different operating system.
- They may have a slow connection, a small screen,
a text-only screen, etc.
- They may not speak or understand fluently
the language in which the document is written.
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
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 readibility 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:
This document addresses some aspects of user interface that directly
impact accessibility, including device-independence, accessible
product documentation, and configurability.
However, the more general
topic of accessible user interfaces for computer software
exceeds the scope of this document. 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 user agent must allow users to control the style (colors,
fonts, speech rate, speech volume, etc.) and format of a
document. Users must also be able to access both primary and alternative representations of content.
The user agent must enable navigation among different parts of
the document: links, form controls, tables, etc., in an input
device-independent manner. Navigation should follow any
tabbing order that has been specified by the
author. How tabbing order is defined typically depends on markup
language (e.g., the "tabindex" attribute in HTML).
The user agent should provide users with information
about views of a document, document structure, document
summary information, and events to help the user
remain oriented. Perhaps more importantly, the user agent
should 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.
Not all user agents satisfy the above principles natively, so they must make information
available to assistive technologies. Even when a user agent
implements a feature natively, it should make information available to
other software. Information must be made available through
interoperable and standard interfaces and generally according to
operating system conventions (except where those conventions hinder
accessibility).
Note. In general, software should be designed,
installed, configured, and documented according to operating
environment conventions.
This document refers to three concepts:
- Guideline
- A guideline is a general principle of accessible design.
A guideline addresses the question "What
accessibility issues should I be aware of?"
- Checkpoint
- A checkpoint is a specific way of satisfying one or
more guidelines. While checkpoints describe verifiable
actions that may be carried out by the user agent
developer, implementation
details are described elsewhere. A checkpoint answers
the question "Where specifically can I improve accessibility?"
- Technique
- A technique is an implementation of one or more checkpoints in a
given language (e.g., HTML, XML, CSS, DOM, ...). A technique
answers the question "How do I do that in HTML or SMIL
or CSS...?"
This document lists guidelines and the checkpoints that satisfy
them.
The associated Techniques
Document provides in-depth descriptions of the same checkpoints
and examples of how to implement the checkpoints using HTML, CSS, and
more. Please note that the Techniques Document will be updated more
regularly than the current document in order to keep up with changes
in technology.
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]).
This document defines two categories of
conformance in order to promote a standard of accessibility
within, and interoperability between, two important classes of user
agents - graphical desktop browsers and dependent assistive
technologies. The two categories of conformance are:
The conformance definitions use the following terms:
- 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.
- 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
discusses some content that affects accessibility
and should be recognized as such.
- 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.
In order to conform as a desktop graphical user agent,
the user agent must do all of the following:
- Satisfy all the Priority 1 checkpoints
listed in this document that
apply to that class of user agent, and
- Satisfy those checkpoints
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 Priority 1 checkpoints
listed in this document that
apply to that class of user agent.
- Satisfy those checkpoints
natively
unless the checkpoint explicitly indicates
that it may be satisfied through communication with other software.
This section defines terms used in this document.
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. Some attributes are integral to document accessibility
(e.g., the "alt", "title", and "longdesc"
attributes in HTML).
An element's rendered
content is that which a user agent renders for the
element. Often, this is what lies between the element's start and end
tags. However, some elements cause external data to be rendered (e.g., the
IMG element in HTML). At times, a browser may render the value of an
attribute (e.g., "alt", "title" in HTML) in place of
or in addition to the element's content. Rendering is not limited to only visual displays,
but can also include audio (speech and sound) and tactile displays
(braille and haptic displays).
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.
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.
User agents generally offer several mechanisms for
referring to parts of content in a view: focus,
selection, and insertion point.
The user focus designates an active
element in a document. Which elements
are active depends on the document language.
In HTML documents, for example, active
elements include links, form controls, elements with a
value for the "longdesc" attribute, and elements with
associated scripts. 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.
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.
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).
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.
Certain types of content (e.g., images, audio, video, applets,
etc.) may not be accessible to all users, so user agents must ensure
that users have access to author-supplied alternative
representations of content. The Techniques Document describes the
different mechanisms authors may use to supply alternative
representations of content. Please also consult the
Web Content Accessibility Guidelines ([WAI-PAGEAUTH]).
User agent accessibility requires that the user be able to install
the software, learn about its features, configure it, and find help
when necessary.
Documentation must be accessible so that users may learn about
software features, notably those that relate to accessibility. 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.
- 4.1.1 [Priority 1]
- Ensure that the software may be installed
in a device-independent manner using any
supported input and output devices.
- 4.1.2 [Priority 1]
- Ensure that all product documentation
conforms to the Web Content
Accessibility Guidelines ([WAI-PAGEAUTH]).
- 4.1.3 [Priority 2]
- Describe product features known to promote
accessibility in a section of the product documentation.
- 4.1.4 [Priority 2]
- Allow the user to configure the user agent in
named profiles that may be shared (by other users
or software).
See also checkpoint 7.2.4.
One of the keys to an accessible user interface is
device-independence. Users must be able to interact with a user agent
(and the document it renders) using the supported input and output
devices of their choice. Input devices may include pointing devices,
keyboards, braille devices, head wands, microphones, 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.
- 4.2.1 [Priority 1]
- Ensure that all functionalities offered by the user agent
interface are available through all supported input devices.
These include the installation procedure, access to
documentation, and software configuration.
- 4.2.2 [Priority 1]
- 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.
- 4.2.3 [Priority 1]
- Ensure that the user can activate the
links and form controls in a
document in an input device-independent manner.
For those user agents that support keyboard input, the input
methods must be accessible. 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. Configurability is vital to accessible keyboard input.
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.
- 4.3.1 [Priority 2]
- Allow the user to configure keyboard access to
user agent functionalities.
Configuration includes the ability to specify single keystroke commands as
well as commands that require keystroke combinations.
- 4.3.2 [Priority 2]
- Ensure that user can find out about all
keyboard bindings (e.g., through menus).
- 4.3.3 [Priority 2]
- Provide a mechanism to render the
presence of a keyboard binding for an
active element.
Users must be able to turn on and off support for features that may
interfere with accessibility. User agents are only expected to provide
this control for content that it recognizes. See also guideline 5.1.
- 4.4.1 [Priority 1]
- Allow the user to turn on and off rendering of images.
- 4.4.2 [Priority 1]
- Allow the user to turn on and off rendering of
background images.
- 4.4.3 [Priority 1]
- Allow the user to turn on and off rendering of video.
- 4.4.4 [Priority 1]
- Allow the user to turn on and off rendering of sound.
- 4.4.5 [Priority 1]
- Allow the user to turn on and off rendering of captions.
- 4.4.6 [Priority 1]
- Allow the user to turn on and off animated or blinking
text.
- 4.4.7 [Priority 1]
- Allow the user to turn on and off animations and
blinking images.
- 4.4.8 [Priority 1]
- Allow the user to turn on and off support
for scripts and applets.
- 4.4.9 [Priority 1]
- Allow the user to turn on and off support
for user style sheets.
- 4.4.10 [Priority 1]
- Allow the user to turn on and off support
for author style sheets.
- 4.4.11 [Priority 2]
- Allow the user to turn on and off rendering of frames.
- 4.4.12 [Priority 1]
- Allow the user to turn on and off support for
spawned windows.
- 4.4.13 [Priority 3]
- Allow the user to turn on and off automatic page forwarding.
- 4.4.14 [Priority 3]
- Allow the user to turn on and off automatic page refresh.
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.
The user must be able to control the colors, fonts and other
stylistic aspects of a document and to override (have final control
over) author styles and user agent default styles. 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:
- 5.1.1 [Priority 1]
- Allow the user to control font family.
- 5.1.2 [Priority 1]
- Allow the user to control font size.
- 5.1.3 [Priority 1]
- Allow the user to control foreground color.
- 5.1.4 [Priority 1]
- Allow the user to control background color.
- 5.1.5 [Priority 1]
- Allow the user to control selection
highlighting (e.g., foreground and
background color).
- 5.1.6 [Priority 1]
- Allow the user to control focus highlighting
(e.g., foreground and
background color).
See also checkpoints 5.3.6 and
5.3.7.
Checkpoints for applets and animations:
- 5.1.7 [Priority 2]
- Allow the user to control animation rate.
Checkpoints for video.
- 5.1.8 [Priority 1]
- Allow the user to control video frame rates.
- 5.1.9 [Priority 2]
- Allow the user to start, stop, pause, and rewind video.
- 5.1.10 [Priority 1]
- Allow the user to control the position of captions.
Checkpoints for audio:
- 5.1.11 [Priority 1]
- Allow the user to control audio playback rate.
- 5.1.12 [Priority 2]
- Allow the user to start, stop, pause, and rewind audio.
- 5.1.13 [Priority 2]
- Allow the user to control audio volume.
Checkpoints for speech:
- 5.1.14 [Priority 1]
- Allow the user to control speech playback rate.
- 5.1.15 [Priority 2]
- Allow the user to control speech volume, pitch,
gender and other articulation characteristics.
Checkpoints for changes to the user interface:
- 5.1.16 [Priority 2]
- When new windows or user
interface components are spawned, allow the user to control
window size and position.
User agents must give users access to author-supplied alternative representations of content
(descriptions of images, captions for video or audio, etc.) since
some users cannot perceive the primary content due to a disability or
a technological limitation (e.g., browser configured not to display
images). See also guideline 5.3.
General checkpoints:
- 5.2.1 [Priority 1]
- Ensure that the user has access to
alternative representations of content (e.g.,
the value of "alt" in HTML or SMIL,
the resource designated by "longdesc", or
the content of OBJECT in HTML 4.0, the "summary" attribute
for tables in HTML, etc.).
- 5.2.2 [Priority 2]
- When no alternative text representation has
been specified, indicate what type of object is present.
- 5.2.3 [Priority 3]
- When alternative text has been specified explicitly
as empty (i.e., an empty string), render nothing.
Checkpoints for audio:
- 5.2.4 [Priority 1]
- If a technology allows for more than one caption or
description track for audio, allow the user to
choose from among tracks.
- 5.2.5 [Priority 2]
- Allow the user to specify that captions for audio be
rendered at the same time as the audio.
Checkpoints for video:
- 5.2.6 [Priority 1]
- 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.
- 5.2.7 [Priority 1]
- If a technology allows for more than one audio
track for video, allow the user to
choose from among tracks.
- 5.2.8 [Priority 1]
- Allow the user to specify that
captions or descriptions for video be rendered at the same
time as the video.
- 5.2.9 [Priority 2]
- Allow the user to specify that
audio descriptions of video be rendered at the same
time as the video.
For all link navigation or searching, the focus is moved to the target link.
See also guideline 4.3.
- 5.3.1 [Priority 2]
- Allow the user to navigate sequentially among
links. See also checkpoint 6.2.1.
- 5.3.2 [Priority 1]
- Allow the user to search for a link in the current
document based on its link text.
- 5.3.3 [Priority 1]
- Allow the user to search for a link
based on its attribute values.
- 5.3.4 [Priority 1]
- Allow the user to move the focus to
a link based on its integer (tabbing-order) position.
- 5.3.5 [Priority 2]
- Provide the user with information about
the number of links in a document.
- 5.3.6 [Priority 3]
- Provide a mechanism (e.g., through
style sheets) to distinguish visited links
from unvisited links.
- 5.3.7 [Priority 3]
- Allow the user to specify (e.g., through
style sheets) that images used in links
must have borders.
The following checkpoints refer to links
to long descriptions of content. See also guideline 5.2.
- 5.3.8 [Priority 2]
- Allow the user to navigate among
elements with associated long descriptions.
See also checkpoint 6.2.1.
- 5.3.9 [Priority 2]
- Allow the user to search linked long description text
(i.e., in another document). In case of a match,
the focus should be moved to the link in the
current document.
Tables were designed to structure relationships among data. In
visual media, tables are often rendered on a two-dimensional grid, but
this is just one possible interpretation of the data. On the Web, the
HTML TABLE element has been used more often than not to achieve a
formatting effect ("layout tables") rather than as a way to structure
true tabular data ("data tables")
Layout tables cause problems for some screen readers and when
rendered, confuse users. Even data tables can be difficult to
understand for users that browse in essentially one dimension,
i.e. for whom tables are rendered serially. Large tables pose
particular problems since remembering cell position and header
information becomes more difficult as the table grows.
User agents facilitate browsing by providing access to specific
table cells and their associated header information. How headers are
associated with table cells is markup language-dependent.
Tabular navigation is required by people with visual impairments
and some types of learning disabilities to determine the content of a
particular cell and spatial relationships between cells (which may
convey information). If table navigation is not available users with
some types of visual impairments and learning disabilities may not be
able to understand the purpose of a table or table cell.
- 5.4.1 [Priority 1]
- Provide access to the contents of a specific table cell.
- 5.4.2 [Priority 1]
- Provide access to header information for
a specific table cell.
- 5.4.3 [Priority 2]
- Allow the user to navigate among tables in a document.
See also checkpoint 6.2.1.
- 5.4.4 [Priority 1]
- 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).
- 5.4.5 [Priority 2]
- Allow the user to search for a table cell
based on its contents or header information.
- 5.4.6 [Priority 2]
- Allow the user to select a table cell and
find out its row/column coordinates in the table.
- 5.4.7 [Priority 2]
- Allow the user to find out the dimensions
of a table.
- 5.4.8 [Priority 2]
- Allow the user to find out
the number of tables in a document.
For all form control navigation or searching, the focus is moved to the target form
control. See also guideline 4.3.
- 5.5.1 [Priority 2]
- Allow the user to navigate among
form controls within a form.
See also checkpoint 6.2.1.
- 5.5.2 [Priority 2]
- Allow the user to navigate among forms in a document.
See also checkpoint 6.2.1.
- 5.5.3 [Priority 1]
- Allow the user to search for a form
control based on its text content.
- 5.5.4 [Priority 1]
- Allow the user to search for a form
control based on its attribute values.
- 5.5.5 [Priority 2]
- Provide the user with access to any label
explicitly associated with a form control.
- 5.5.6 [Priority 2]
- Provide the user with information about
the number of forms in a document.
- 5.5.7 [Priority 2]
- Provide the user with information about
the number of controls in a form.
- 5.5.8 [Priority 3]
- Allow the user to request to be prompted before
a form is submitted.
Orientation - the sense of where one is within a document or series
of documents - is fundamental to a successful Web experience. Visual
clues that help orientation often abound:
- proportional scroll
bars indicate how much of the document has been read
- frames suggested relationships among documents
- graphical site maps describe page organization
Not all users can use visual orientation clues, however, so user
agents must complement them with other mechanisms, including:
- Contextual information about the
document or views (e.g., how many views, how
whether the document has finished loading, how much of the
document has been read).
- Summary information about specific elements (e.g.,
the dimensions of a table).
- Context information about elements in the document (e.g.,
a cell's position in a table, the number of links in a document).
- Navigation sequentially among parts of the document
(e.g., headers).
- Searching for information in the document.
- Alerts when events occur during browsing (e.g.,
a window opens, a script is executed, etc.).
See also guidelines 5.3,
5.4, and 5.5.
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.
- 6.1.1 [Priority 1]
- Provide a mechanism for highlighting and
identifying (through a standard interface where
available) the current view.
- 6.1.2 [Priority 1]
- Provide a mechanism for highlighting and
identifying (through a standard interface where
available) the user selection.
- 6.1.3 [Priority 1]
- Provide a mechanism for highlighting and
identifying (through a standard interface where
available) the current focus.
- 6.1.4 [Priority 2]
- Ensure that when the selection changes, it is
in the viewport after the change.
- 6.1.5 [Priority 2]
- Ensure that when the focus changes, it is
in the viewport after the change.
- 6.1.6 [Priority 1]
- Allow the user to navigate views (notably those
with frame viewports). Navigating into a view makes it the
current view.
- 6.1.7 [Priority 1]
- Keep track of the user's point of regard in each
view and restore it when the user returns to the view.
- 6.1.8 [Priority 2]
- Provide the user with information about
the number of viewports.
- 6.1.9 [Priority 2]
- When a document is loaded or when requested by the
user, make available document summary information.
- 6.1.10 [Priority 2]
- Provide the user with information about how much of
the document has been viewed (i.e., where the
point of regard is with respect to the beginning
of the document).
- 6.1.11 [Priority 3]
- Provide the user with information about document loading
status (e.g., whether loading has stalled,
whether enough of the page has loaded to begin navigating, whether
following a link involves a fee, etc.)
Hierarchical navigation (through the document tree) is useful for
efficiently navigating the major topics and sub-topics of a document.
- 6.2.1 [Priority 1]
- Allow the user to navigate sequentially
among all active elements
in the document. See also checkpoints
5.3.1, 5.3.8, 5.4.3,
5.5.1, and 5.5.2.
- 6.2.2 [Priority 2]
- Allow the user to view a document outline constructed
from its structural elements (e.g., from header and list elements).
- 6.2.3 [Priority 2]
- Allow the user to navigate the document tree.
- 6.2.4 [Priority 2]
- Allow the user to navigate sequentially among headers.
- 6.2.5 [Priority 2]
- Allow the user to navigate sequentially among
block elements (e.g., paragraphs, lists and list items, etc.)
- 6.2.6 [Priority 2]
- Allow the user to search for
content. In case of a match, move the
selection to the content.
It is important to alert users, in an output device-independent
fashion, when important events occur during a browsing session. 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.
- 6.3.1 [Priority 1]
- Allow the user to navigate among
elements with associated event handlers.
- 6.3.2 [Priority 2]
- Alert the user when scripts or applets are executed.
- 6.3.3 [Priority 3]
- Provide information about document changes
resulting from the execution of a script.
Many types of software: assistive technologies,
scripting tools, automated test engines, etc., benefit from
having access to user agent information.
A user agent that supports a language should implement the
accessibility features for the language. The techniques
document lists the accessibility features of the following
languages, defined by W3C specifications:
- 7.1.1 [Priority 1]
- Support accessibility features defined by
W3C Recommendations for HTML.
- 7.1.2 [Priority 1]
- Support accessibility features defined
by W3C Recommendations for CSS.
- 7.1.3 [Priority 1]
- Support accessibility features defined
by W3C Recommendations for SMIL.
When a user agent communicates with other software (dependent user
agents, the operating system, plug-ins), must do so through applicable
interfaces. To promote interoperability, open standards should be used
wherever possible.
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.
- 7.2.1 [Priority 1]
- For desktop graphical browsers.
Export programmatic interfaces to ATs and
follow operating system conventions to do so
(e.g., Microsoft Active Accessibility, Sun Microsystems
Java Accessibility).
- 7.2.2 [Priority 1]
- For desktop graphical
browsers.
Ensure that exported interfaces conform to
those specified by a W3C DOM
Recommendation.
- 7.2.3 [Priority 1]
- Use standard interfaces defined for the operating system.
- 7.2.4 [Priority 2]
- Follow operating system conventions
and accessibility settings in
user interface design, configuration (including
configuration profiles), product
installation, and documentation.
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, 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
- [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-PAGEAUTH]
- "Web Content Accessibility Guidelines", W. Chisholm,
G. Vanderheiden, and I. Jacobs, eds.
The latest Working Draft of these guidelines for designing
accessible Web pages and sites is available at:
http://www.w3.org/TR/WD-WAI-PAGEAUTH.
- [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