WCAG 1.0 7.1 Until user agents allow users to control flickering, avoid causing the screen to flicker. [Priority 1] Note. 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). Section 508 - § 1194.22