Web Content Accessibility Guidelines a guide to the accessibility requirements
2 Operable

2.3.2 Three Flashes

Conformance level: AAA
Criterion released in WCAG version: 2.0

Official description of the success criterion

Web pages do not contain anything that flashes more than three times in any one second period.

What to do?

Avoid content that flashes more than three times in one second.

Why is it important?

Prevents seizures in users with photosensitive epilepsy.

More about this criterion elsewhere