How do i resize my body frame like this site? is there a template like vbulleting.org

[24hourForum.com]

How do i resize my body frame like this site?

My forum is showing on all the window.. i want it to only show the body just like this forum, the background shows up in the edges.. how can i do that to my site?

[Lynne]

Styles & Templates > Style Manager > locate your style > StyleVars in drop-down > Main Table Width (pixels or percentage) > set it to a percentage like 90%