Avoid objects that may cause the screen to blink |
WAI / WCAG 1.0 Priority 2 checkpoint 7.2
Issue Description The page contains objects (scripts, applets, HTML objects) that might cause blinking on the screen. If this is the case, it is best to modify or remove them.
How to check Check if the object causes blinking (i.e. a constant on/off behavior of part of the screen) that does not stop and that cannot be stopped by the website visitor. If so, modify the object behavior so that no blinking occurs, or so that the visitor has the means to stop it from blinking. Alternatively ,set the object to blink a couple of times and then come to rest.
Issue Explanation The object (script, applet, HTML objects) causes blinking and the user of the browser will in no way be able to stop this on/off behavior. This blinking behavior is very distracting to the eye, and will make it very difficult to concentrate on the task of reading the information in the page or in filling in the form contained in the page.

The consequences will be even more significant on users that suffer from cognitive disorders, as they will have a very hard time concentrating on the page content. Consider also users of screen magnifiers, who may read a small portion of the page that overlaps with the blinking text. In these cases, a large part of the magnified screen will blink; again making it very hard for these users to concentrate on the task.

Consider that, in a sense, everyone is cognitively disabled when under stress. For example, when buying an e-ticket for a flight from a kiosk in a very noisy and crowded airport, with a long line of people waiting for the same kiosk, most people will be unable to fully concentrate on the task. A blinking element in the page will not help the user to complete the purchase.