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Computing and Information Services

Elements to avoid

There are a number of features supported by some browsers that can cause accessibility problems for some users. Avoiding use of these features is recommended.

Web Accessibility Initiative Guidelines

This page explains how to meet:

  • Guideline 7.2: "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)."
  • Guideline 7.3: "Until user agents allow users to freeze moving content, avoid movement in pages."
  • Guideline 7.4: " Until user agents provide the ability to stop the refresh, do not create periodically auto-refreshing pages."
  • Guideline 7.5: "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."
  • Guideline 10.1: "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.".

Reasons for following these recommendations

Certain behaviour possible through HTML or scripts can cause large accessibility problems for certain users. Even for the majority of users, breaking these guidelines can be disorientating and a usability issue.

How to follow these guidelines.

Avoiding blinking and moving content is a trivial matter. In some cases animation may be useful, however, for example as part of an applet. In this case, provide an alternative non-animated version, and allow users to choose between the two.

There is also no need to use the <meta> tag to refresh a page automatically - if the content is regularly updated (and they are made aware of this), then users will use the refresh function in their browser to check for updates. The Opera browser has the capability to automatically reload a page at the user's preferred interval.

There is also often no need to use the <meta> tag to redirect automatically to another page. If you are able to use server-side scripting such as PHP, then do so, as this allows the redirection to take place on the server (and in many browsers, automatically update incorrect bookmarks).

To avoid the use of 'meta refresh':

  1. Avoid changing the location of pages if possible
  2. Use server-side scripts to perform the redirect (Server administrators: configure the server to perform a 301 (permanent) redirection to the new location).
  3. Have a link to the new page and no redirect.

Finally, pop-up windows should not be used, as they can disorientate users, and be difficult to find when using a screen magnifier. Also, many browsers do not support the scripting required to use them. Opening a new window with the attribute (set link target to _blank in the Dreamweaver properties) has many of the same problems. Users are always able to choose to open a new window for a page if their browser supports it - fewer browsers have an 'open in same window' option.

New windows can also interact badly with tabbed browsers (some browsers open a new tab instead, some open a new window and tab set) and cause the "back button" to break. This can be especially confusing for users if their browser is running maximised, as the new window may appear over the old window and not be noticed. This can make it much harder for users to return to the original page.

Checking

Automatic accessibility checkers can check for the presence of <meta> tags used to refresh or redirect, and for code that opens new windows. However, they cannot usually check scripts or applets for pop-ups, or moving or blinking content, and this must therefore be checked manually.