It came about when Rolf Harris was convicted recently. It was decided to use his name as an item of jest. The thumb is the one he used whilst painting, to get true perspective.
Why do we usually see an abbreviation such a rofl and not a smiley?Etc all mean, in general, you find the post funny.
Means thanks or great
If you havent found the smiley button yet it below the B button on the task bar of your reply box