A Design Question

[elefekt]

I was wondering where can I add a border along the side of the forum to make a rounded style.

Since I know I am confusing I want something like:

http://www.vbskinz.com/vb3/index.php?styleid=11

the white that encloses the forum and the gray thats on the end. Basically I want to add two borders to each side.

Thanks.