Well, I honestly think the internet in general has made people worse at their native languages. Back when I was still working for Domino's, my boss called a couple of us into the office. He actually had someone submit a job application that was filled with your typical internet shorthand and leetspeak.
I'll admit I'm not the smartest guy in the room. I'd like to think that most employers are reasonable enough to forgive a minor spelling error here and there. Unless you're being hired as a proofreader, then spelling is the least of my concerns. But, to actually have full on leetspeak in your job app? Yeah, that son of a bitch went straight to the trash once we all got done laughing at it.
Mika, if you're writing something and need help in regards to spelling and the like, I'd suggest the following link. It's what I put my rough drafts of my Broken World, Broken Souls chapters into before additional refinement and posting to FF.net ^_~
Granted, I don't know if it works with anything other than English, but there you go.
http://www.grammarcheck.net/editor/