It's not the short form of anything. It is illiteracy or just plain lazy, that's all. If you cannot be bothered to write properly here, do not expect to have any interaction with the rest of the forumers who do display some intelligence, unlike yourself.
Doesn't your keyboard have at lease 88 keys? Probably has 101 like most so there is no reason not to use proper English here. Also, unlike a mobile phone with limited capacity, you do not have that problem here. So try to appear a little bit intelligent. Even if you are out on school holidays at the moment and mommy has let you use the PC it's helps to practice as you are obviously in need of it.