(Steal these buttons)
Best of Craigslist, Grammar Lesson #1, Your vs. You're:
Your - belonging to you, e.g. - Your ass is ignant and shit. You're - contraction from You + are (standing for, ironically, "you are"), e.g. - You're an ignant ass.
You're - contraction from You + are (standing for, ironically, "you are"), e.g. - You're an ignant ass.