Please read this as many times as you need to for it to sink in.
Your is possessive. Like Mine. For example: Your illiterate blog.
You're is a contraction of YOU ARE. You're an effing idiot if you say things like "Your stupid." because it should be YOU'RE STUPID! If you cannot substitute the words "YOU ARE", then use YOUR.
Listening to: Katy Perry - I Kissed A Girl