Making Accessible Websites for the United Nations

Page Design: Visual Elements

No Flickering, Blinking or Moving Content

WAI Definition (Checkpoints 7.1, 7.2 and 7.3)

Until user agents allow users to control flickering, avoid causing the screen to flicker.

Until user agents allow users to control blinking, avoid causing content to blink (i.e., change presentation at a regular rate, such as turning on and off).

Until user agents allow users to freeze moving content, avoid moving elements in pages.

Explanation

Avoid visual elements which can cause the screen to flicker, move or blink.

Rationale

Screen flickering and blinking can trigger epileptic seizures in people suffering from photosensitive epilepsy.

Older screen readers also have problems with blinking or moving content and may crash or be unable to render the content at all.

Furthermore, it is difficult to read some text that is flashing or moving, or to read the content of a page when something else is flashing or moving on that page. Users read at different speeds and moving text does not accommodate those differences. Blinking or moving text will frequently distract visitors from what is important on the site.

Finally, the <blink> and <marquee> tags are not part of the HTML specification and, as such, should be avoided.

Technique

Do not create elements that flicker or blink.

Validation

Test

Check the page content.

Success Criteria

Ensure that the page does not contain elements that flicker, blink or move.

There are no brusque changes in luminosity or flash effects.