Well other than this is NOT a java forum, this is for c# and theres a .net web forum too.. The first thing is that you would have to use some form of ajax type thing as you would need to ask the db if the usernames there - but best advice, ask in a more apprioriate forum.
Rashakil Fol commented: He didn't mention Java. -2
Run.[it] commented: Absolutely clueless!!!!! +0
scru commented: rude -1