...Well, I'm not exactly sure how to explain it, because I don't completely understand it myself. But basically, 1337=l33t=leet, which is some weird internet way of writing. Or something like that, at least. Anyway, I checked with a friend of mine, and to call someone 1337 (or l33t) usually means you're saying that they're cool, but in this case, the person is probably saying that you spend too much time on line, you're dorky, etc. So basically, this jerk is insulting you. And just for the record, I don't agree with this jerk.