Background problem and resize templete wide

Hello! I just got the "hot furniturestore" and I want to have a background image in all page but the original site extends in all the wide of the page, the template says that the template width is 960px. but I still cant change it.

I try to change it in layout.css
body {
margin:0;
padding:0;
font-family:"Trebuchet MS", Arial, Helvetica, sans-serif;
line-height:20px;
bbackground:url(../images/backgroundt.jpg) top center no-repeat;
}

but it still looks withe in the sides and in the low of the page the images repeat in x, can you pleas help me?? I attatched the image.



Thanks for your help!!

Im sorry the light went down and the topic duplicate, I dont know how to erase one, thanks again!