i hav no problum wit theyr speling!!!
Nah, just kidding. I do have a problem with it. If someone is angry and is screaming text-based, better do it right so you won't look like a rabid monkey.
And god help you if you start the 'Ub3r7331Hax0rz' shit. I don't care if he knows the way to cure cancer. If he talks like that, all his arguments are invalid at that point, there's no way I can see that person as an intelligent, educated being.
Typos are fine. I bet I've made some myself right now. I'm from The Netherlands, the rules on capital letters and punctuation are a bit different here. But come on! They're, their, there. There is a difference! (pun not intended)
I do get mad when I see... well 'i'. The one in lower case. It either means: 'I am foreign so I don't give a shit!' or: 'The Shift key is too far away from my pinky!'
Edit: I actually edited some sentences, even the one with the bad grammar because I wanted it to look worse. -_-