dog pees when he sees me

Question
I have a 4 month old rottie who is very good dog he will stay in his crate while im at work 6 hours and not pee. But sometimes when i come home and walk to his crate he starts peeing why can he hold it so long then pee in front of me? Also i had company over and twice he urinated once on my carpet and once as my freind was petting him is this just cause hes a pup and excitemnet is overtaking him. Thank you  

Answer
Many dogs eventually outgrow it, but you can reduce it by building the dog's confidence up.  Start with obedience training.  The key to most behavior problems is approaching things using the dog's natural instincts.  Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog.  Life is much easier if the 2 legged pack members outrank the 4 legged ones.  You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at http://www.dogsbestfriend.com/  As you praise the dog for following your commands, it will build its confidence.  

Play tug of war with the dog and lose.  However at the end of the game, take the rope or toy and put it up, less the dog becomes confused about who is top dog.
Ropes from the pets' store quickly turn to hazardous shreds.   Ones I made
lasted much better.   Go to a hardware or home center that sells rope by the
foot.  Buy 2' of 3/4" poly rope.   Melt the ends, and tie  knots in it.   Get
them as tight as possible, put it in a vise and pound it with a hammer.  Watch
carefully, and be ready to discard when it comes apart.