I know where to put the header picture at, but I need help with formatting the page.

I want my page to be 910 pixels accross and i can't find where to change that at.

I also need to know where to change the header height at.

Basically I want the header picture to match the header picture at www.beerants.com.

If I can get this change made then everything will be running the way I want it to run.

The cart is at www.beerants.com/zencart.