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

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1. Don't use the <MARQUEE> element or use javascript to create moving or scrolling text. Screen readers are unable to read moving text. 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.
   
   
2. Don't use the <BLINK> element. A flickering or flashing screen may cause seizures in users with photosensitive epilepsy. Seizures can be 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).