Give users time to respond

Requirement: No event on a Web page can occur without sufficient notice to the user and ample time for the user to exercise some control over that event.

Different users respond to different events at different speeds. While it is sometimes necessary to have a timed event, alerts should be given that event is being timed, and also, sufficient time should be given to users to respond to the warning.

Keep in mind that users with low-vision might employ devices like screen magnifiers. Or for those using a screen reader or a text-only browser, they may take some time just to navigate through a page's initial links. These users may need more time than those who use a typical graphical browser to just reach the alert indicating the timed event.

No automatic client-side page redirection

One such timed event is a client-side page redirection. This is accomplished through of a "Meta refresh" tag in the head section of an HTML page. Developers use this when they replace a page and want to redirect users to the new page.

The problem is some developers try to do too much for the user. They set the page to redirect automatically (refreshes in 0 seconds). Most users will never see the redirection page. However, when they attempt to use their browser's back function, they get caught in a loop because the page backward is a page that automatically kicks them forward.

This same problem can be created by using javascript. This is a common problem as many developers try to check for the presence of a plug-in such as Flash on a user's browser. They use a javascript to check the browser, and then if the browser does not have Flash, they instantly whisk them to a non-Flash page. While the intent is noble, the execution is flawed. Consider giving users the option of selecting a plug-in vs. non-plug-in page, or by using a document.write javascript, you can change just certain elements on the page and not the entire location.

Automatic refreshing should be avoided. If pages are moved, someone's server administrator can configure the server to handle the redirection seamlessly without interfering with the user's browser functions. If you use a redirect page, most people are happy enough to click the URL themselves. Plus, it also helps convey that that page has moved and the user should update his or her bookmarks.

If you must automatically refresh, provide ample time. Consider allowing 20 seconds for every line of text, but again, it is best to avoid refreshing.