YOU'RE [yoor; unstressed yer] contraction of you are: You're certain that's right?
(DEFINITIONS FROM DICTIONARY.COM)
It seems to me that once people get a Facebook, all knowledge of how to use "your" and "you're" goes out the window-- I'm going to solve this with a quick grammar lesson:
If you want to say that something belongs to someone, you use YOUR. Simple as that, this is first grade grammar guys, try to follow along.
If you want to say that someone is something, you use "YOU'RE" because it is the contraction for "YOU ARE".
For example, if someone on Facebook wants to call someone a cauldron bum they should say: "YOU'RE a cauldron bum" because "YOUR a cauldron bum" means...well, nothing, it doesn't make any sense. It isn't even a real sentence.
If someone on Facebook wants to say that someone has a nice chest they should say: "YOUR boobs are hot" (also, please spell "hot" right, people that use "hawt" seriously, are just douche bags). Saying "YOU'RE chest is nice" means, "YOU ARE chest is nice" and once again ISN'T A REAL SENTENCE!
Please guys, try to remember this, because if I see "your" & "you're" misused one more time, I'm going to scream, & we already have enough ear piercing noises in Scholte....
