I was trying to steal the gmail emoticon (you can see it as my favicon), when I noticed something exceptionally strange. You’d think they would use a GIF to make the emoticon, but no, they are using a PNG sprite.
Check out this amazingly tall sprite they use for their emoticon.
It’s always interesting to me to learn how Google does their HTML. I am guessing they did a test and figured out this was more efficient and useful than using an animated GIF?