"z0mg d0000d you're hair is s000 awe3summ brahhhhh! your the awesomest doooood!!!!!11!!!!1!!!one!!!one!!"
Although some people have realized the true difference between the two words, let me explain the differences to those who still have not.
The word "Your" is used when showing possession.
The word "You're" is used when describing the person you are communicating with.
Your: Your hair. Your terrible grammar. Your small penis.
You're: You're the person with bad grammar. You're a faggot.