If I am asking is because I dont know,
I tried searching with firebug, but I am not an specialist on css design, I dont remember what valued and files edited exactly... allways is just try and error, like lots of users.
Anyone who got the idea, can have the kindness and tell me how to do it..
What css to edit, and what values I have to add to make postbit and forumdisplay rounded.
Thank you very much.