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Designing for Accessibility - Other Elements

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Moving, Scrolling Flickering Content and Pages

§ 508 1944.22: (j)Pages shall be designed to avoid causing the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz.

Moving, blinking, flickering and scrolling text and images can make page content inaccessible to many people with disabilities. Animations and movement can be distracting for people with cognitive disabilities; screen readers cannot perceive scrolling text; screen flickers with frequencies of greater then 2 Hz and lower than 55 Hz can cause seizures. To ensure accessibility:

  • Provide a method so that the user can pause, stop or override moving/ scrolling objects. If movement is essential to the design, use style sheets with scripting to create the desired effect and provide a method to turn off the feature.
  • Do not use the <blink> or <marquee>element s.
  • Do not auto-refresh pages. With each refresh, the focus moves to the beginning of the page and screen-readers start to re-read the page from to the top.

Timed Responses

§ 508 1944.22: (p) When a timed response is required, the user shall be alerted and given sufficient time to indicate more time is required.

Often, for security and other reasons, pages /transaction are designed to "expire" after a specified time. Some people with disabilities are unable to read, move around or interact with web pages fast enough to perform prescribed task in a set amount of time. When a timed response is required:

  • Alert the user that a process requires a timed response and inform them of the time constraints.
  • Provide a method by which the user can request for additional time or complete the transaction without time constraints
  • Notify the user when a process is about to time-out and provide a prompt to request additional time.

Text Only Page

§ 508 1944.22: (k) A text-only page, with equivalent information or functionality, shall be provided to make a web site comply with the provisions of this part, when compliance cannot be accomplished in any other way. The content of the text-only page shall be updated whenever the primary page changes.

Use Text-only alternative page as a last resort. When using text-only page

  • Provide a clear link to the alternative page.
  • Ensure that the alternative page is accessible.
  • Ensure that the alternative page has equivalent information or functionality.
  • Update the alternative page as often as you update the original page.

To help web-designers meet this guideline, NC State has licensed Text-Transcoder, a server-based tool that dynamically parses the content of a web page into a "Text Only" page, eliminating the need to maintain dual pages. However, this method does require web-developers to create pages to XHTML standards.

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