Techniques for WCAG 2.0

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F50: Failure of Success Criterion 2.2.2 due to a script that causes a blink effect without a mechanism to stop the blinking at 5 seconds or less


Technologies that support script-controlled blinking of content.

This failure relates to:


Scripts can be used to blink content by toggling the content's visibility on and off at regular intervals. It is a failure for the script not to include a mechanism to stop the blinking at 5 seconds or earlier. See SCR22: Using scripts to control blinking and stop it in five seconds or less (Scripting) for information about how to modify the technique to stop the blinking.


Failure Example 1

The following example uses script to blink content, but the blink continues indefinitely rather than stopping after five seconds.

Example Code:

<script type="text/javascript">
// blink "on" state
function show()
	if (document.getElementById)
	document.getElementById("blink1").style.visibility = "visible";
	settime-out("hide()", 450);
// blink "off" state
function hide()
	if (document.getElementById)
	document.getElementById("blink1").style.visibility = "hidden";
	settime-out("show()", 450);
// kick it off
<span id="blink1">This content will blink</span>



For each instance of blinking content:

  1. Determine if the blinking stops in 5 seconds or less.

Expected Results

If #1 is false, then the content fails the Success Criterion.

Techniques are Informative

Techniques are informative—that means they are not required. The basis for determining conformance to WCAG 2.0 is the success criteria from the WCAG 2.0 standard—not the techniques. For important information about techniques, please see the Understanding Techniques for WCAG Success Criteria section of Understanding WCAG 2.0.