[amjadz4]

Originally Posted by haothiencz

You just can make a style fixed or fluid that way.

It's good with default style but for some style with images it require also adding

value repeat-x for the bg and forumhead etc...

well true, but once you set your theme to be of a fixed size and in case any image go out of the table for example a large forum header image you can either use dynamic resizing using timthumb.php or just resize the image. But this is very unlikely and happens rarely. Theme designers should make their theme compatible for every scenario.