Remove Background, or other stuff

Hi, I made this forum to test some things for my site, and I'm trying to get rid of the background. Any help?
http://googlesclubtester.forumotion.com/

Have you checked the ACP --> Display --> Pics Management --> Advanced Mode --> General / Explore --> Background Picture (Page)

Yeah, that doesn't work. The background has been added through CSS, and I don't know which code it is

Look for this in your CSS:

Code:

body {
    background: url("http://i66.servimg.com/u/f66/13/46/75/82/header33.png") no-repeat scroll center top rgb(160, 199, 63);

Thanks, it worked

But there's still some of the old background showing, how can I remove that?

Please post a screenshot with the areas circled that still have the background that you want to remove.