WAI Accessibility Guidelines: User Agent
W3C Working Draft 19-Oct-1998
- This version:
- Latest version:
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- Related documents:
- User Agent Techniques
- Jon Gunderson <firstname.lastname@example.org>
Ian Jacobs <email@example.com>
This document provides guidelines to user agent manufacturers (producers
of browsers, players, etc.) for making their products more accessible to
people with disabilities. Since accessible design is good design,
following these guidelines will improve Web browsing for able-bodied users
This document is part of a series of accessibility documents published
by the 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)
This document has been produced as part of the
W3C WAI Activity, 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
This document is available in the following formats:
- A plain text file:
- HTML as a gzip'ed tar file:
- HTML as a zip file (this is a '.zip' file not an '.exe'):
- A PostScript file:
- A PDF file:
In case of a discrepancy between the various formats of the
specification, http://www.w3.org/WAI/UA/WD-WAI-USERAGENT-19981019 is considered
the definitive version.
Please send comments about this document to the public mailing list:
Each guideline is classified according to the
following rating system:
- [Priority 1]
- This guideline must be implemented by user
agents as a built-in feature or through compatibility with assistive
technology, otherwise one or more groups of users with disabilities will
find it impossible to access information.. Implementing
this guideline is a basic requirement for some groups to be able to use
- [Priority 2]
- This guideline should be implemented by user agents
as a built-in feature or through compatibility with assistive
technology, otherwise one or more groups of users will find it difficult
to access information.. Implementing this guideline will
significantly improve access to the Web.
- [Priority 3]
- This guideline may be implemented by user agents as
a built-in feature or through compatibility with assistive
to make it easier for one or more groups of users to access
information. Implementing this guideline will improve access to the
In this document, the guidelines are grouped by
topic. Generally, a guideline may be "implemented" by one or more
techniques. The priority levels for techniques mirror those for
guidelines in weight. The priority level of a technique indicates how
important it is as a means of satisfying the associated guideline.
For example, a Priority 3 technique must be
implemented to provide accessibility, while a Priority 3 technique,
may be implemented to provide further assistance.
The following general principles of accessible user agent design
underlie the guidelines listed in this document:
All users must be able to access all functionalities of a user agent.
Users access these functionalities through controls
(menus, buttons, keyboard shortcuts, etc.).
Controls should be arranged in a manner consistent with their importance.
- The user interface should be accessible to all users.
- The interface must be easy to understand regardless of the
user's experience, knowledge, language skills, or current concentration
level. Where the interface is not accessible, inaccessible functionality must
be made available through accessible controls.
Part of accessible access includes
prompting the user effectively for input
and providing useful feedback during and after each task.
- The user interface must accommodate a wide range of
individual preferences and abilities.
- Therefore, user interfaces
must have redundant controls for the same functionality
(e.g., menu, mouse, and keyboard equivalents) and
must avoid, for example, mouse-only controls. Redundancy includes
offering visual as well as aural representations of a control.
User agents must also
allow users to customize and configure the controls to meet their needs.
- The user agent must render information in accessible forms.
- The user agent must allow users to control the style of rendering
(colors, fonts, etc.), and the format of rendering (e.g., serialization
of tables). Users must also be able to access both primary
and alternative content.
- The user agent must facilitate navigation and orientation
on a page and between pages.
- The user agent must allow keyboard navigation at all times.
The user agent should provide Web page orientation information (the number
of links on a page, the number of form controls, the number of images,
etc.) so the user can quickly grasp content and context.
- The user agent must be compatible with
third-party assistive technologies.
The guidelines in this document rely on a certain number of common
document and user agent features. The following sections define
terms that describe these features.
These definitions have been worded to make the guidelines usable
but also to allow some freedom of interpretation.
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
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 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
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 whether
the document is being rendered on the screen, on paper, through
speakers, or on a braille device. Style information (e.g.,
font and color information) 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 value given to a property by a user agent when it is
started up is called the property's default value.
Browsers 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
Current values may come from documents, style sheets, scripts, or the
user interface. Values that come from documents, their associated style
sheets, or via a server are called author
styles. Values that come from user interface settings, user
style sheets, or other user interactions are called
A browser offers one or more views of
a document. A view is a way of perceiving a document: a full
view, a summary view, a filtered view, etc. The user views the document
through a viewport, which may
be a window, frame, a piece of paper, a magnifying glass, etc.
Each view has only one viewport, but several views may have the same
viewport (e.g., the same browser window may be used for
different views of different documents as one browses the Web).
The dimensions of the viewport may restrict the view
of a document. User agents generally allow users to
move the viewport over the complete view (e.g., through
scrollbars or some other panning mechanism).
Some of the guidelines below involve tracking the user's
regard in the view. The point of regard describes
where the user's attention lies in the view. Generally, the
point of regard is constrained to the part of the view
exposed by the viewport. As the guidelines below state, user
agents should avoid displacing the viewport away from the
user's point of regard as this can disorient users.
When a document is rendered aurally (or serially
in generally), the point of regard is defined as that which
is "currently" being rendered. Identifying the point of
regard in a two-dimensional space is a more difficult
task as users may be "looking at" any point on the screen or
Depending on the guideline, the user's point of regard
in a two-dimensional space may be identified by:
- The insertion point.
- In an editor/browser, the insertion point is the
location where text editing takes place.
- The user selection
- The user selection is defined here as the part of a document
(possibly spanning several elements) identified for
cut/copy/paste operations. 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 may have only one user selection. When
several views co-exist, each may have a user selection, but only one is
active, called the current user
The user selection may be rendered specially (e.g., visually
Highlighted text is often used by third-party assistive technologies to
indicate through speech or Braille output what the user wants to read. Most
screen readers are sensitive to highlight colors.
Third-party assistive technologies may
provide alternative presentation of the selection through speech,
enlargement, or dynamic Braille display.
The user selection may be used, for example, to identify the
"current cell" of a table that the user is navigating.
- The user focus.
- The user focus designates an element that the user
may interact with. Such elements are called
In HTML, active elements are defined as 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 meaning 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 only one focus.
When several views co-exist, each may have a focus, but only one is
active, called the current focus.
Both the current focus and the current user selection must be in the
same view, called the current view.
Certain events (document loading
or unloading events, mouse press or hover events, keyboard events, etc.)
may cause the browser to perform tasks. For instance, when a mouse button
is released over a link, the link is activated, possibly causing a new
document to be loaded into the browser. Events may occur due to user
interaction or through other means such as scripting. Note.
The interaction of HTML, style sheets, the Document Object Model
and scripting is commonly referred
to as "Dynamic HTML" (DHTML). However, as there is no
W3C specification that formally defines DHTML, the guidelines will
only use the term scripting.
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 content.
The techniques document
describes the different mechanisms authors may use to supply
An independent user agent only
requires the source document (and associated style sheets, etc.) to render
the document's content. It may use an accessibility API to retrieve
information about a document.
A dependent user agent relies on
the output of some other user agent in order to render a page. Dependent
user agents include screen magnifiers and screen readers, both of which
rely on the visual output of another user agent.
In order to access a document, some users may require that
it be rendered in a manner vastly different from that which
the author intended. Users who are color-blind may not
be able to perceive certain color combinations. Users with
weak vision may require large fonts. Sightless users may
require audio rendering.
User agents must therefore allow the user to have the final say
- The document's style (e.g., fonts, colors, etc.)
- The document's formatting: whether the document is
presented textually, graphically, serially,
aurally, tactiley, or some combination of these.
- The document's content. This means whether "normal" content or
alternative content or both are rendered.
The following guidelines address user control over rendering.
The user must be able to control the colors, fonts and other
stylistic aspects of a document and to override author styles
and user agent default styles. Otherwise,
users who are blind,
have low vision, 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.
- Allow the user to override author
styles and browser defaults, and
in particular those properties affecting:
font face, font size, foreground and background colors, background
images, user selection highlight colors, and
user interaction (e.g., hover styles). [Priority 1] [Go to user-preference]
- Allow the user to turn off blinking text or images for all cases when
the user agent knows that text or images are blinking. [Priority 1]
[Go to user-blink]
- Allow the user to specify custom settings in profiles
that may be shared (by other users or software). Preferably, this should
be done via style sheets. Furthermore, for
convenience, users should be able to name groups of settings and be able
to apply them all at once (e.g., by selecting a group by name from a
menu). This should also be achieved with style sheets. [Priority 3]
[Go to user-portable]
- Allow the user, through a keyboard command, to switch between browser
default values and the
user profile. [Priority 3] [Go to user-switch]
User agents must give users access to author-supplied
(descriptions of images, video clips, sounds, applets, etc.)
Some users cannot perceive the primary content due to
a disability or a technological limitation (e.g., browser configured
not to display images) If users cannot access
alternative content, users who are blind,
have low vision, some types of learning
disabilities, or any user who cannot or has
chosen not to view the primary representation of information
will not understand the intention or content of the page.
- Give the user access to alternative content (e.g., the
"alt" or "longdesc" attributes in HTML or SMIL, the
content of OBJECT in HTML 4.0).
[Priority 1] [Go to alt-content]
- Allow the user to specify that alternative text and/or
long descriptions be rendered in place of primary content.
[Priority 1] [Go to alt-rendering]
- When no alternative text representation is available,
indicate what type of object is present. [Priority 1]
[Go to alt-no-alt]
- Allow users to hide the display of D-links used to provide access to long description information.
[Priority 3] [Go to alt-d-link]
Techniques for multimedia objects
In the following guidelines, multimedia players may
be stand-alone software or plug-in applications.
- Allow the user to identify and turn on/off
text captions of audio.
[Priority 1] [Go to multimedia-caption]
- Allow the user to control the size, color, and
background color of captions.
[Priority 1] [Go to multimedia-rendering]
- Allow the user to identify and turn on/off audio
descriptions of video. [Priority 1] [Go to multimedia-descriptions]
- Ensure that text media objects may be
identified by third-party assistive
technologies. [Priority 1] [Go to multimedia-compatibility]
- Make accessibility-related information
from the OS user profile
available to the media player. [Priority 1] [Go to multimedia-os-options]
- Allow users to reposition captions. [Priority 2] [Go to multimedia-positioning]
- Allow users to control (dynamically) the rendering rate of audio
media objects. [Priority 2] [Go to multimedia-speed]
Techniques for other types of objects
- Allow the user to specify that alternatives to a
script be rendered (e.g., in HTML, the content of NOSCRIPT).
[Priority 1] [Go to alt-no-script]
- Allow the user to specify that alternatives to a
frame be rendered (e.g., in HTML, the content of NOFRAMES).
[Priority 1] [Go to alt-no-frame]
- Allow the user to specify that alternatives to a
table be rendered (e.g., the value of the "summary" attribute
on TABLE in HTML 4.0).
[Priority 1] [Go to alt-table-summary]
By offering several formatting solutions to users, user agents
allow them to select the solution most adapted to their needs.
For instance, users with screen readers will have difficulty
understanding some tables whose cell contents exceed one line.
In this case, if the independent user agent can serialize
the table (i.e., render it one cell at a time), the screen reader's
output will not cause confusion. Similarly, some users may require
that a user agent present an outline view
of a document so they may have an easier time navigating the
- Allow users to specify that tables be formatted serially,
based on the type of information in the table.
[Priority 1] [Go to table-serialization]
- Allow users to view a document outline constructed from its
structural elements (e.g., from header and list elements
in HTML). [Priority 2] [Go to document-outline]
Orientation - the sense of where one is within a document or series
of documents - is fundamental to a successful Web experience.
Authors may contribute to orientation through sight maps,
navigation bars, visual associations between documents using
frames, etc. User agents also facilitate orientation with
proportional scrollbars on viewports.
Not all users can use visual orientation clues, however, so
user agents must complement them by:
- Providing support for a
point-of-regard for people relying on
- Providing summary information about certain elements
(e.g., active elements)
in all or part of a document.
- Supporting, when appropriate for the target medium,
speech and tactile identification of elements.
If users cannot orient themselves to the types of
elements in a document, users who are blind, have
low vision, some types of learning
disabilities, or any user who cannot or has chosen not
to view the author's representation of information will have
incomplete knowledge of the content of the document.
- When a document is loaded or when requested by the
user, make available document summary information.
[Priority 2] [Go to orientation-summary]
- Provide a mechanism to indicate visually the presence of
attribute defined for a link or form control. [Priority 2]
[Go to orientation-accesskey]
- Provide the user with audio feedback about document loading
information. Such information includes whether loading has stalled,
whether enough of the page has loaded to begin navigating, whether
following a link involves a fee, etc. [Priority 3]
[Go to orientation-audio-feedback]
- Provide a mechanism to distinguish visited links from unvisited
links. [Priority 3] [Go to orientation-visited-links]
- Allow the user to specify that images used in links must have
borders. [Priority 3] [Go to orientation-link-borders]
- Provide a mechanism for assistive technologies to identify which
elements have associated scripts. [Priority 1]
[Go to orientation-scripting]
- Provide information when a script is executed.
[Priority 2] [Go to orientation-elements]
- Provide information about document changes resulting from the
execution of a script. [Priority 1]
[Go to orientation-scripting-changes]
Users that are viewing documents through serial 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 difficultly 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.
- Provide the user with information about how much of the document has
been viewed. [Priority 2] [Go to orientation-doc-position]
- Provide the user with information about which table cell is the
current table cell.
[Priority 2] [Go to orientation-table-position]
- Support the "rel" and "rev" attributes defined
in HTML ([HTML40],
section 12.1.2). [Priority 2] [Go to compatibility-html-rel-rev]
For people with visual impairments, it is important that the
point of regard
remain as stable as possible. For instance, when returning
to a document previously viewed, the user's previous point
of regard on the document should be restored. 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.
Disturbing the user's point of regard may
cause problems for users who have movement impairments, who are blind, who have low vision, who
have certain types of learning disabilities, or
for any user who cannot
or has chosen not to view the authors representation of information
- Provide a mechanism for highlighting and identifying the
current view, focus, and user selection.
[Priority 1] [Go to orientation-doc-view]
- Keep track of the user's point of regard in each view
and put it within the viewport when the user returns
to the view. [Priority 1]
[Go to orientation-previous-focus]
- Allow the user to specify that a view's focus should follow changes
in the viewport. [Priority 1] [Go to orientation-focus-follow]
- Allow user to be prompted before spawning a new window. [Priority 2]
[Go to orientation-spawning-browser]
- [Ed. How is this identified?]
Allow the user to turn on and off automatic page forwarding. [Priority 3]
[Go to orientation-page-forwarding]
There are different ways a user may want to navigate while
browsing the Web, including:
- By changing the position of the viewport
(e.g., by scrolling down the page).
- By shifting focus from one active element to the next of the
same type (e.g., from link to link).
- By navigating among documents.
For all of the navigation
techniques described below, the user agent must
allow the user to navigate via the keyboard.
Often, users wish to navigate a
linear sequence of elements or related documents (frames)
sequentially, e.g., to the next or previous document.
If sequential navigation is not
available users with some types of movement impairments,
visual impairments and learning disabilities
may not be able to access the links and controls in a document.
- Allow the user to navigate sequentially
between links (including elements with long descriptions) or
between form controls in the same view.
[Priority 1] [Go to navigation-sequentially]
- Allow the user to navigate views (notably
those with frame viewports).
Navigating into a view makes it the current view. [Priority 1]
[Go to navigation-views]
For comfortable browsing, users may with to navigate
to a particular element of a certain type. For instance,
in a document with many links, sequential navigation
will require a great number of key strokes to reach a desired
element. In addition to being wearisome, this may be physically
difficult for some users. Without direct access (e.g, by element
identifier or element
position), users with some types of movement
impairments, visual impairments and learning
disabilities may not be able to access the links and
controls and other elements in a document efficiently.
[Ed. In the following text searches, what
happens when the search succeeds? Is the user selection updated?
The focus? Is the viewport moved?]
- Allow the user to search for an element in the
current document by its text content.
[Priority 1] [Go to navigation-search]
- Allow the user to search for a link in the
current document based on its link text or alt text.
[Priority 2] [Go to navigation-search-links]
- Allow the user to move the focus directly to a specific
link in the current document. [Priority 2] [Go to navigation-link-list]
- Allow the user to move the user selection directly to
a specific element in the current document
that is not an
[Priority 2] [Go to navigation-direct-elements]
- Allow the user to search for an element in the
current document by its
alternative content (e.g., the value of
the "alt" and "title" attributes).
[Priority 2] [Go to navigation-search-alt]
- Allow the user to include the text contents of any long
descriptions in the text searches described above.
However, if matched text occurs within a long description,
focus should be moved to the first element in the main document
for which the long description was written.
[Priority 3] [Go to navigation-search-longdesc]
Hierarchical navigation (through the document tree)
is useful for quickly navigating the
major topics of a document. Topical navigation (section by section)
conveys significant information about the organization of a document.
If hierarchical navigation is not
available users with some types of movement impairments,
visual impairments and learning disabilities
may not be to access the links and controls on a page efficiently nor
understand the topics and topic relationships within a document.
- Allow the user to use the keyboard to navigate the document
tree. [Priority 2] or [Priority 3] [Go to navigation-hierarchical]
Tabular navigation is required by people with visual
impairments and some types of cognitive disabilities
to determine the content of a particular cell and spatial
relationships between cells (which may convey information).
If sequential 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.
- Provide a mechanism for designating the
of a table. The current table cell
may be designated with the user selection.
[Priority 1] [Go to table-current-cell]
- Allow the user to navigate among table cells
(notably left/right within a row and up/down within a
column). [Priority 1] [Go to navigation-table]
- Allow the user to navigate to a specific table cell
through its row/column coordinates, header information,
or its content.
[Priority 1] [Go to navigation-cell]
Users must be able to emulate events when their user agents
do not allow them to trigger events in the anticipated way. For
instance, users without mice must be able to trigger the same
events that users with mice can trigger. Furthermore, some
users may not realize when an event occurs because the event has
an effect the user cannot perceive (e.g., a visual effect). The
user agent must be able to inform users when events take place
and to a certain extent, what has been the effect of the event.
- Allow the user to navigate elements with associated
scripts (through the document language). Both
sequential and direct navigation should be possible.
[Priority 1][Go to nav-scripts]
- Allow the user to trigger events through redundant means.
Users must be able to trigger mouse events with the keyboard
[Priority 1][Go to nav-trigger-event]
Ideally, able-bodied as well as disabled users would be aware of user
agent features that improve accessibility and experienced peers
could share their knowledge with new users.
In reality, most able-bodied peers do not know
about features that improve accessibility or do not find them useful for
their own use and so ignore them.
Consequently, users with disabilities must
find help information on their own to optimize the user agent to their
preferences. This information must be readily available and in accessible
The organization and layout of accessibility feature controls has a
major impact on helping users with disabilities find and learn about
configuration options and the range of browsing options available to them.
If the user agent interface does not offer coherent and
for configuring the software, users with disabilities may not be
able to optimize the user
interface to their preferences.
- Allow users to configure accessibility features easily and directly.
[Priority 2] [Go to visibility-configuration]
- Furnish predefined accessibility profiles for
common disabilities. [Priority 2] [Go to visibility-profiles]
Keyboard access can be a boon to users having any of several
disabilities. The more apparent the keyboard commands are to all
users, the more likely it is that new users with disabilities
ill find them. Readily available
information about keyboard access is crucial to its effective use by users
with visual impairments and some types of movement
impairments, otherwise a user with disabilities may not think
they can accomplish a particular task or may
try to use a very inefficient
technique with a pointing device, like a mouse.
- Display keyboard navigation shortcut commands in customizable menus.
[Priority 2] [Go to visibility-menu-commands]
- Provide a list of all keyboard commands (organized by key or by
topic) in an accessible format. [Priority 2] [Go to visibility-keyboard-doc]
Documentation must be available in accessible formats for people with
print impairments. If users with visual impairments and
learning disabilities and movement impairments
that limit the use of paper documents cannot access on-line or printed
documentation efficiently, they may not know about user agent features or
be able to use the user agent efficiently or at all.
- Provide a description of accessibility features in the on-line
documentation. [Priority 2] [Go to visibility-online-accessinfo]
- Provide a description of accessibility in printed documentation.
[Priority 2] [Go to visibility-print-access]
- Ensure that the online documentation interface is accessible. [Priority 2]
[Go to visibility-online-accessible]
- Provide print and on-line information in alternative formats for
people with print impairments. [Priority 2] [Go to visibility-documentation-alt]
User agents typically operate in within an operating system and in the
context of other standards. user agents need to be compatible with
The following guidelines apply to user agents that implement Cascading
Style Sheets (see CSS, level 1 and
CSS, level 2). Cascading Style Sheets may be part
of a source document or linked externally.
Stand-alone style sheets are useful for implementing user
profiles in public access computer environments where several
people use the same computer. User profiles allow for convenient
customization and may be shared by a group.
- Completely implement Cascading
Style Sheets, level 1 [Priority 1] [Go to compatibility-css1]
- Allow the user to turn off author
styles represented by author style sheets. [Priority 1]
[Go to compatibility-css2-style]
- Allow the user to adjust default values
represented by browser style sheets. [Priority 1]
[Go to compatibility-css2-default]
- Support the :before and :after pseudo-elements as defined in CSS2 ([CSS2],
section 12.1). These pseudo-elements generate content that can help
orient the user by identifying the element that is being spoken or
presented in Braille by third-party assistive technology. [Priority 1]
[Go to compatibility-css2-pseudo]
- Support the 'outline' property as defined in CSS2 ([CSS2],
section 18.4). Outlines may be used to customize the focus display (see
also orientation information). [Priority 1]
[Go to compatibility-css2-outline]
- Allow the user to specify user styles
through style sheets (see [CSS2], section 6.4).
[Priority 2] [Go to compatibility-css2-user]
- Implement the !important rule as defined in CSS2 ([CSS2],
section 6.4.2). These rules offer a way for users to override
author styles and
browser defaults [Priority 2]
[Go to compatibility-css2-important]
- Support aural cascading style sheets (see [CSS2],
chapter 19) for the auditory presentation of documents. [Priority 2]
[Go to compatibility-css2-aural]
- Support the "longdesc" attribute defined for IMG elements ([HTML
4.0], section 13.2). This attribute may be used to attach
additional descriptive information to images.
[Priority 1] [Go to compatibility-html-longdesc]
- Support the CAPTION element ([HTML40],
section 11.2.2) for rich table captions. [Priority 2]
[Go to compatibility-html-caption]
- Support the "summary" attribute for TABLE ([HTML40],
section 11.2.1) for table summary information. [Priority 2]
[Go to compatibility-html-summary]
- Support the NOSCRIPT element ([HTML40],
sections 18.3.1 and 16.4.1) for accessible alternatives to scripts.
[Priority 2] [Go to compatibility-html-noscript]
- Support the NOFRAMES element ([HTML40],
sections 18.3.1 and 16.4.1) for accessible alternatives to frames. [Priority 2]
[Go to compatibility-html-noframes]
- Support the "lang" attribute ([HTML40],
section 8.1). [Priority 3] [Go to compatibility-html-lang]
- Support the "tabindex" attribute ([HTML40],
section 17.11.1) for assigning the order of keyboard navigation within a
document. [Priority 3] [Go to compatibility-html-tabindex]
- Support the "accesskey" attribute ([HTML40],
section 17.11.2) for assigning keyboard commands to
active elements such as links, and form
controls. [Priority 3] [Go to compatibility-html-accesskey]
Most operating systems have standard user interface controls and
application programming interfaces that support third-party assistive
technology in providing alternative user interfaces. Many operating
systems also have built-in accessibility features that should be tested
for compatibility with user agents.
- Standard OS Controls/Menus/Dialog boxes [Priority 1]
[Go to compatibility-os-controls]
- Built-in Accessibility Options [Priority 1] [Go to compatibility-os-built-in]
- Accessibility Application Programming Interfaces [Priority 1]
[Go to compatibility-os-accessibility-api]
Many thanks to the following people who have contributed through review
and comment: Paul Adelson, James Allen, Denis Anson, Kitch Barnicle,
Harvey Bingham, Judy Brewer, Kevin Carey, Wendy Chisholm, Chetz Colwell,
Daniel Dardailler, Neal Ewers, Geoff Freed, Larry Goldberg, Markku
Hakkinen, Chris Hasser, Kathy Hewitt, Phill Jenkins, Leonard Kasday,
George Kerscher, Marja-Riitta Koivunen, Josh Krieger, Greg Lowney, Scott
Luebking, William Loughborough, Napoleon Maou, Charles McCathieNevile,
Masafumi Nakane, Charles Opperman, Mike Paciello, David Pawson, Helen
Petrie, David Poehlman, Michael Pieper, Jan Richards, Greg Rosmaita, Liam
Quinn, T.V. Raman, Robert Savellis, Constantine Stephanidis, Jim Thatcher,
Jutta Treviranus, Claus Thøgersen, Steve Tyler, Gregg Vanderheiden,
Jaap van Lelieveld, Jon S. von Tetzchner, Ben Weiss, Evan Wies, Chris
Wilson, Henk Wittingen, and Tom Wlodkowski.
If you have contributed to the UA guidelines and your name
does not appear please contact the editors to add your name to the list.
- "CSS, level 1 Recommendation", B. Bos, H. Wium Lie, eds.
The CSS1 Recommendation is available at:
- "CSS, level 2 Recommendation", B. Bos, H. Wium Lie, C.
Lilley, and I. Jacobs, eds. The CSS2 Recommendation is available at:
- "WAI Resources: CSS2 Accessibility Improvements", I. Jacobs
and J. Brewer, eds. This document, which describes accessibility
features in CSS2, is available at:
- "Document Object Model (DOM) Level 1 Specification",
V. Apparao, S. Byrne, M. Champion, S. Isaacs, I. Jacobs, A. Le Hors, G. Nicol,
J. Robie, R. Sutor, C. Wilson, and L. Wood, eds. The DOM Level 1 Recommendation
is available at:
- "HTML 4.0 Recommendation", D. Raggett, A. Le Hors, and I.
Jacobs, eds. The HTML 4.0 Recommendation is available at:
- "WAI Resources: HTML 4.0 Accessibility Improvements", I.
Jacobs, J. Brewer, and D. Dardailler, eds. This document, which
describes accessibility features in HTML 4.0, is available at:
- "Synchronized Multimedia Integration Language (SMIL) 1.0
Specification", P. Hoschka, editor. The SMIL 1.0 Recommendation is
- "WAI Accessibility Guidelines: Page Authoring", G.
Vanderheiden, W. Chisholm, and I. Jacobs, eds. These guidelines for
designing accessible documents are available at:
- Techniques for
"WAI Accessibility Guidelines: Page Authoring", G.
Vanderheiden, W. Chisholm, and I. Jacobs, eds. This evolving
document is available at: