If u r l337 enuf ull und3rst4nd wu7 pwned is.
...
It's just part of the Internet culture, my friend. It just basically means that someone has been beaten, in a game, a contest, or anything of that sort. There's a whole world of "Internet/IM speak" out there, some of it just a way of talking in "code" to be cool, and some of it shortens words to make them easier/faster to type over instant messengers. Every generation seems to develop their own "language" of sorts, this is just the newest incarnation.
Hope that helps,
Scott