Like many other "0r" words (like bitchz0r, or hax0r, or sux0rz), this has an unknown origin. But it can be traced back to "lolsaur".
If
you are a true lamer, use it. If not, AVOID IT AT ANY COST, or people will start to think
you're a moron.
Person1:
something REALLY funny
Person2: OMG lolz0rrrr!!!!111
Person1: yaaaaaa bitchz0r die cuz i am teh hax0rz
Person1:
kekeke
Person2:
kekeke! lolz0r!!!11
Person1: Hi.
Person2: lolz0r
Person1: ?
Person2: lolzor!!
Person1: O.o
Person2: lolz0r!!!111 kekeke omg lolz0r!!!