Avoid Flicker

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Avoid Flicker

Avoid Flicker

  • Section 508 requires that "pages shall be designed to avoid causing the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz."
  • Areas not specified by this standard:
    • Movement
    • Blinking
    • Scrolling
    • Auto-updating objects or pages
  • You should:
    • Ensure that users can pause or stop any moving, blinking, scrolling, or auto-updating objects on a page
    • NOT use the blink or marquee elements

Often people find animation distracting and confusing. However, individuals can turn off animations in Internet Explorer using Tools / Internet Options / Advanced, and there scroll down to Multimedia and uncheck Play animations. Using Netscape Navigator or Microsoft Internet Explorer, you can stop animated gifs with the Stop button on the tool bar or the Escape key.

People with photosensitive epilepsy can have seizures triggered by flickering or flashing in the 4 to 59 flashes per second (Hertz) range with a peak sensitivity at 20 flashes per second as well as quick changes from dark to light (like strobe lights). This concern caused the Access Board to include the following standard:

Pages shall be designed to avoid causing the screen to flicker with a frequency greater than 2 Hz and lower than 55 Hz.

Other areas not specifically covered by this standard are movement, blinking, scrolling, and auto-updating objects or pages.

Some people with cognitive or visual disabilities are unable to read moving text quickly enough or at all. Movement can also cause such a distraction that the rest of the page becomes unreadable for people with cognitive disabilities. Screen readers are unable to read moving text. People with physical disabilities might not be able to move quickly or accurately enough to interact with moving objects.

Animated images can be a nuisance to many people, so you must ask yourself if there is anything to be gained in having them in your Web site.

You should:

  1. Ensure that the user can pause or stop any moving, blinking, scrolling, or auto-updating objects or pages. If you must have movement on the page, use style sheets with scripting to create the effect you want. This allows users to turn off or override it more easily.
  2. Do not use the blink or marquee elements.
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