English is (almost) a second language for me, but I've been teaching the thing for eleven years now, and this 'Internet spelling' of words and phrases is slowly but surely becoming an epidemic.
Apart from (relatively simple) mis-spellings like 'tonite' or 'nite', there have been numerous sightings of the use of 'there' as a substitute for the possessive 'their', and also of the possessive 'your' instead of the contracted verb form 'you're'. In sentences llike this:
Your right to make them carry there backpacks the rest of the way.
I haven't determined the origin of this practice, at first I thought it was simply an americanism, limited to teen web surfers, but I'm beginning to see it in other varieties of English, and in print, and the average age of the users seems to be going up, and up, and up. (Could be the same people growing, though...)