Just a moment ago I wanted to send a link to the latest XKCD comic through Windows Live! Messenger. I sent it just well, along with a comment, but the next second I was suddenly sharing the picture (in messenger), and the tooltip text was underneath it in a way I hadn't seen before.
So... WTF? How did this happen? Is XKCD website special somehow? Or can I make my website like that too with some special tags or something? I didn't see anything standing out in the markup.
Added: (Open picture for a bigger view)