Avoid Flicker
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This rule is easy. Anything that causes the screen to flash or flicker must be avoided. While the rules says that anything causing the screen to flicker between 2Hz and 55Hz, it is difficult to measure the frequency so avoid all flicker.
Things that cause flicker:
- Animated GIFs
- <MARQUEE> or <BLINK> HTML tags
- Certain applications of JavaScript
Flicker can cause people with photosensitive epilepsy to have seizures and it can also be distracting for all uesrs, but particularly those with certain types of learning disabilities. Highlight important information with other methods besides things that flicker.
