[TECH] What is the WCAG stance on blinking?

The WCAG HTML techniques document says, "Do not create blinking content 
with the blink element. ".   There is an editorial note that asks, "If 
this is because we disapprove of blink we should provide an alternative 
technique. If it's because we disapprove of blinking, we should say so and 
point to something. "

While blinking can be very annoying, when used carefully it is useful to 
bring attention (for sighted users, at least) to a particular item on the 
page.  I certainly agree that the blink element should not be used.  It is 
not in the HTML 4.01 nor XHTML 1.0 DTD and thus not supported by all 
browsers.  What about blinking controlled via JavaScript?  As long as the 
blinking does not violate the General Flash Threshold (see Guideline 3.2 
Level 3 Success Criteria) I don't think WCAG should ban its use.  We can 
at least provide a JavaScript technique for "responsible blinking" that 
includes a way to turn it off. 

The attached file has examples of using JavaScript and CSS to create a 
blinking text element.   The file loads with blinking turned off.  Use the 
buttons to toggle blinking on and off.  The JavaScript blinking technique 
was tested and works in IE 6, Firefox 0.9.2, Mozilla 1.71 and 1.8a3, and 
Opera 7.54 all on Windows 2000. It also works with HPR 3.04 (beta), JAWS 
4.51, and WindowEyes 4.5 sp3.  The screen readers always seem to speak the 
blinking text even though the JavaScript  implementation alternates the 
style from visibility:hidden to visibility:visible.

If we agree that blinking is acceptable, I'll submit this as a JavaScript 
technique. 

(Note: There are several issues with the CSS text-decoration:blink 
technique used in this file - I'll discuss that in a post responding to 
issue #1021.)

-becky




Becky Gibson
Web Accessibility Architect
                                                       
IBM Emerging Internet Technologies
5 Technology Park Drive
Westford, MA 01886
Voice: 978 399-6101; t/l 333-6101
Email: gibsonb@us.ibm.com