the ultimate comeback to "no u". The way the letter w is pronounced sounds like "double u" so saying no w in response to no u gives an almost instant win
Jarold II: your gay Jarold I: no u Jarold II: no w
It now stands for the activity which surrounds most of the time in which the web is browsed - Wanking While Watching (another video stream or live webcam) or, Wanking While Waiting (for the next lot of porn to download).
(For the Brit-ignorant, Wanking is the same as jerking-off/Whippin Mr Zippy/Polishing the PurplePink Pole, over here in Limey-Land.)
In terms of a differnt style of generation of the phrase :3 as in a animeish style version of the :3 hamster face Expression being really happy, or a big grin its usually followed with the "!" mark with how happy you are..