Standard J: Flickering Elements

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

Why is this provision necessary?

This provision is necessary because some individuals with photosensitive epilepsy can have a seizure triggered by displays that flicker, flash, or blink, particularly if the flash has a high intensity and is within certain frequency ranges.

How can flashing or flickering elements be identified?

Use your best judgment as to how much flickering your web site has. If it looks like too much, it probably is a problem. Flashing or flickering elements are usually added through technologies such as animated gif's, Java applets, or third-party plug-ins or applications. Java applets and third party plug-ins can be identified by the presence of <APPLET> or <OBJECT> tags. You also should not use JavaScript, or the <BLINK> or <MARQUEE> tag to make text blink or move.