http://www.techcrunch.com/2009/10/03/gmail-now-with-favicons/

<<I loaded up Gmail this morning expecting to see the usual assault on my inbox, when something new caught my eye. Apparently, Google has started inserting favicons, the little icons that many browsers put next to a website’s URL or bookmark, next to messages.>>

Umm...this is pretty old.

http://mail.google.com/support/bin/answer.py?hl=en&ctx=mail&answer=151545