Well, it's both a grammatical error *and* a spelling mistake, since 'it's' is a noun and verb contraction and 'its' is a possessive pronoun. They mean totally different things. But I would be willing to let that one slide, myself.
I wasn't going to do this, but I'll go ahead and sign up. I know it has already started. If you can find a mistake I made when it started yesterday, I'll count it as a kill unless rules say otherwise. I do not want to cause a problem since I failed to sign up at the right time.