i'm trying to make a account but it wont let me

www.yahoo.com<< on that page i goto free mail: Sign Up then the free yahoo 1

ID may consist of A-Z, a-z, 0-9, underscores, and a single dot (.)<<--- that under where u put the id u want

i try to make this Mr.YChat and i get this

Yahoo! ID may contain only letters, numbers underscores and a single dot (.).

GOD i done what it say i even scan 4 the id 2 see if some1 else got it and no1 got it can some1 tell me how to make a id