You're right k-troop. But like a golf swing, I never do something without thinking it through clearly (though you can't tell from my handicap). I rarely think "you're" but type "your". Different strokes, different folks.
I should add that with regards to the title of this thread, "grammar" is a noun while "grammatical" is an adjective. Thus, the phrase "grammatical errors," rather than "grammar errors," is actually correct.