YOU'RE vs.YOUR

This is a real pet peeve with me. You're means: YOU ARE. Your does not. 

 Incorrect usage:  "Hope your still in a good mood." or "Your a nice guy,"or still: "Is this you'res?"
If you don't see anything wrong with the above sentences then this is the time to review.
http://www.wikihow.com/Use-You%27re-and-Your
Mind you, I am far from a grammar expert, in fact, I get worse and worst confused often enough, and a few others such as, lie and lay.
A good idea is to see which ones we have trouble with and get some knowledge about it online as the above link provides. :)