Example for Checkpoint
7.1 - Until user agents allow users to control it, avoid causing the screen to flicker.

Slide 60 of 120
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Priority 1

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).

Of course, we can't show you an example of an image or text blinking at 20 flashes per second or we could be accused of trying to bring on an seizure.

The point is: be careful when designing animated .gif images or other refreshing content.

Up one level To Checkpoints for Guideline 7.
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Introduction: Overview Guidelines: Overview Checkpoints: Overview Examples: Overview

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Chuck Letourneau & Geoff Freed

W3C Web Accessibility Initiative

Copyright © 2000 W3C