Background Image Help

[Chaos Residue]

What CSS file am I supposed to be editing? I edited vbulletin.css and changed it from the default:

background:{vb:stylevar doc_background};

to this:

background:{vb:stylevar doc_background};
           {position:absolute};
           {height:100%};
           {width: 100%};
           {margin:0};
           {padding: 0};

Nothing seemed to change. Did I edit the wrong code? Or did I just do it incorrectly?