[jrajav]

I had to test in most of my installed browsers before I found one that actually animated the icon - Firefox. Chrome, Safari, and Opera have all decided (rightly, you'll probably agree) that allowing animated favicons is not a good idea.

[fyi80]

Chrome has a hideously awful alternative though: The tab icon throbs when AJAX updates a page (Gmail, etc), regardless of the web developer or user's preferences.