World Wide Web Consortium (W3C) Web Accessibility Initiative

User Agent Support for Accessibility

Last official modified date:
$Date: 2005/08/11 21:28:53 $
First Pass at an Update (17 July 2007)
Last modified by: Gregory J. Rosmaita 2007/07/31 21:20 UTC
Send comments/addition to:

About this page

The Web Content Accessibility Guidelines 1.0 contains 13 checkpoints that require content developers to create pages in a particular manner "until user agents" support a particular feature. This page documents user agent support for those checkpoints. This page includes additional Resources for User Agent support.

Throughout this document, UAGL refers to the Techniques for User Agent Accessibility Guidelines Working Draft of 6 December 1999. These references will be updated to reflect Techniques for User Agent Accessibility Guidelines 1.0 published December 2002.

Note: As of December 2003, the Web Content Accessibility Guidelines Working Group (WCAG WG) has begun testing and gathering information to update this document.

Status of this page

The test results in this document were last updated 8 December 1999. As of December 2003, we are planning to update the information with test results from the most current versions of Opera, Microsoft Internet Explorer (MSIE), Mozilla, Safari, and Lynx. We also intend to include information about assistive technologies (screen readers, screen magnifiers, and voice input software) that address accessibility requirements.

Tests for the User Agent Support Page was developed in conjunction with this document. However, the more recent Draft Use Agent Accessibility Guidelines test suite for HTML 4.01 will be of more use.

Checkpoints from WCAG 1.0

Checkpoint 1.3

Checkpoint text:

Until user agents can automatically read aloud the text equivalent of a visual track, provide an auditory description of the important information of the visual track of a multimedia presentation.

Status [8 December 1999]: Under discussion. [link to GL open issues list once added]

Checkpoint 1.5

Checkpoint text:

Until user agents render text equivalents for client-side image map links, provide redundant text links for each active region of a client-side image map.

Len Kasday created a test page and the results are documented on the WAI Interest Group mailing list.

UAGL Techniques for checkpoint 1.1 discuss how user agents should do this.

Checkpoint 7.1

Checkpoint text:

Until user agents allow users to control flickering, avoid causing the screen to flicker.

Status as of December 1999: Netscape Navigator (versions, platform), Microsoft Internet Explorer (versions, platform), and Opera (versions, platform) allow the user to turn off loading of images, scripts, and applets. Turning these off will allow the user to avoid flicker caused by images, scripts, and applets. For other plug-ins the user can choose not to load the plug-in. However, it would be ideal if users could stop, pause, or step through animations, scripts, or other dynamic content that may cause flicker as discussed in UAGL checkpoint 3.7 and UAGL checkpoint 3.10

Checkpoint 7.2

Checkpoint text:

Until user agents allow users to control blinking, avoid causing content to blink (i.e., change presentation at a regular rate, such as turning on and off).

Status [as of 8 December 1999]: In NN (4.5, Win98) and Opera (3.6, Win98), scripts and style sheets may be turned off separately. They may also be turned off separately with Netscape (4.61, Linux) although turning off scripts has some effect on style sheets. MSIE (5.0, Win98) does not allow the user to turn off style sheets, although user style sheets may override author style sheets. Lynx (2.8, Unix) and Amaya (2.2, Linux) do not support the BLINK element nor style sheets thus no blinking occurs.

Refer to UAGL checkpoint 3.5 and UAGL checkpoint 3.6.

Tests for checkpoint 7.2.

Checkpoint 7.3

Checkpoint text:

Until user agents allow users to freeze moving content, avoid movement in pages.

Status: No information

Refer to UAGL checkpoint 3.5, UAGL checkpoint 3.6, and UAGL checkpoint 3.10.

Checkpoint 7.4

Checkpoint text:

Until user agents provide the ability to stop the refresh, do not create periodically auto-refreshing pages.

Status: No information

Refer to UAGL checkpoint 3.10.

Checkpoint 7.5

Checkpoint text:

Until user agents provide the ability to stop auto-redirect, do not use markup to redirect pages automatically. Instead, configure the server to perform redirects.

Status: No information

Refer to UAGL checkpoint 3.9.

Checkpoint 10.1

Checkpoint text:

Until user agents allow users to turn off spawned windows, do not cause pop-ups or other windows to appear and do not change the current window without informing the user.

Status: No information

Refer to UAGL checkpoint 4.18.

Checkpoint 10.2

Checkpoint text:

Until user agents support explicit associations between labels and form controls, for all form controls with implicitly associated labels, ensure that the label is properly positioned.

Status: No information

Refer to UAGL checkpoint 2.1 and UAGL checkpoint 7.4

Checkpoint 10.3

Checkpoint text:

Until user agents (including assistive technologies) render side-by-side text correctly, provide a linear text alternative (on the current page or some other) for all tables that lay out text in parallel, word-wrapped columns.

Status [as of 8 December 1999]: IBM's Home Page Reader in combination with Netscape Navigator (4.5, Win98) and Henter Joyce's JAWS in combination with Microsoft Internet Explorer (4.0 and higher, Win98) are instances of a browser and assistive technology combination that can linearize a table. Opera (3.6, Win98) allows a user to linearize tables. Lynx (2.81, Unix) renders tables by row. Silas' Gateway and other tools being developed by the ER Working Group [ER-IG] allow users to linearize tables. However, only Microsoft Internet Explorer (4.0 and higher, Win98) with HelpDB and WWW with EmacsSpeak allow a user to navigate within and between the cells of a table.

Status [July 2007]

Refer to UAGL checkpoint 5.2 and UAGL checkpoint 8.1.

Checkpoint 10.4

Checkpoint text:

Until user agents handle empty controls correctly, include default, place-holding characters in edit boxes and text areas.

There are two pieces

  1. older browsers (Netscape 2.0?) did not allow users to navigate into form controls;
  2. older assistive technologies in trying to overcome this issue would only navigate into form controls with content.

Refer to UAGL checkpoint 7.4.

Checkpoint 10.5

Checkpoint text:

Until user agents (including assistive technologies) render adjacent links distinctly, include non-link, printable characters (surrounded by spaces) between adjacent links.

A test case, and some preliminary results are available

Checkpoint 13.6

Checkpoint text:

Group related links, identify the group (for user agents), and, until user agents do so, provide a way to bypass the group.

Status: No information

Resources for User Agent Support

The following resources provide information about user agent support for language features (e.g., HTML, CSS) and accessibility features.
WebReview offers a few browser compatibility charts, including the safe list and the danger list. They also offer several helpful articles about designing style sheets.
Note: As of 7 july 2007, this site redirects to Doctor Dobb's Portal, The World of Software Development; site-specific searches of yielded nothing terribly germane:
The HTML Compendium's domain ( expired on 2 July 2007
The HTML Compendium documents browser support for a variety of browsers on a variety of platforms.
Alternative WebBrowsing
A collection of pointers to information, and where possible, to demonstration versions of alternative browsing method.
The W3C's CSS Test Suite now tests for CSS 2.1 compatibility
The CSS1 Test Suite is provided as a way for vendors and page authors to test their browser's conformance to the CSS1 specification.
WSP - The Web Standards Project
The Web Standards Project is a coalition of web developers and users encouraging standards support in browsers. They have a number of resources documenting support of standards on various browsers and platforms.

Resources for User Agent Support, July 2007


W3C provides the information on this page as a service to the Web community and in good faith. However, due to resource constraints, W3C cannot verify the accuracy of all claims made by developers or users. W3C is not responsible for the content or persistence of non-W3C Web sites linked from this page.

Valid XHTML 1.0! (check it and see)      Valid CSS! (check it and see)