Could I move the background header to the left?

Background header is always at the same position in the left. Could I move it a little bit to the left in order all my tabs keep inside the background area? This is my provisional URL: 209.62.36.13/~aquituev/nueva-alianza/

www.w3schools.com/css/pr_background-position.asp

I found the code for the background in layout.css but, despite I edit the body tag in this way:

body
{
background-image:url('/images/header_bg5.png');
background-repeat:no-repeat;
background-attachment:fixed;
background-position:left;
}

I didn't see a change in the background position of the header. I just would like the header background would be as wide as the tabs of top menu. Would be that possible?
I'm using Architecture template and my URL is: www.aquituevento.com/nueva-alianza/

Thanks

All you need to do is to edit this image www.aquituevento.com/nueva-alianza/templ...mages/header_bg5.png and make it wider. Don't bother with background positioning, you don't need it.

Thank you very much for your patiente.