Jumping back a few posts, to explain what Callum and Jonesey were on about, "leet speak" , sometimes written 1337 or l33t is an abbreviated form of speech which has developed its own bizarre grammatical forms used by computer gamers and other geeky types on chat rooms (I'm sure that'll be disputed). It uses some similar abbreviations to those already used in chat rooms or in text messages, together with deliberate typos such as "teh" (also written "t3h") instead of "the".
The name "leet" stems from the 1980s computer game, "Elite" and online gamers wanted a quick way of chatting to each other. Of course as some people use expletives for emphasis in conversation :k: , the programs often censored out certain words, and so they became deliberately misspelled and replaced letters with numbers of a similar appearance (e.g. 3 instead of e and 4 instead of A) hence some words ostensibly appearing as alphanumerics.
There, thats saved you reading the Wikipedia article

To answer, your next obvious question, "why?", I have absolutely no idea!!
