Acceptable: Replacement for "you"
Unacceptable: Replacement for "yeah"
The first definition is correct, because "ya" is actually how a lot of people pronounce "you" in a casual conversation.
But using it as "yeah" is incorrect and stupid, because nobody in real life pronounces yeah like "ya". The only people who type it that way are people under 25 who are trying to be cool and fit in with the rest of their e-buddies and Myspace losers.
A lot of them make the excuse that it's easier to type "ya" than "yeah". Yeah right. It's just their way of hiding the fact that they're trying to be cool and fit in on whatever board/forum they're posting on.
At least things like "orly" and "kthx" are funny......"ya" is not. It's just dumb.
By the way, expect all my votes to be negative, because they're all mad that I'm right.
P.S. go read a book instead of wasting time surfing the net or playing video games......you might learn something.
Correct: "Can ya give me an example?"
Incorrect: "Ya, sure"