Page/Content Background

After weeks of trying to get a Zen Cart site off the ground, and hitting error after error, I decided to give OpenCart a shot. Wow, what a difference it is on the admin side. I'm hitting a wall, however, on editing the theme colors.

On wide desktops, I'm trying to do a block-style page instead of full width. Added max-width and auto margins to the header and footer, changed the body background, but what I can't find is a container in the stylesheet for the page content. Example image attached.

Any suggestions?

The div ID is dynamically generated for each page.

For example, home page is #common-home, category page is #product-category.

You will need to add each of the IDs into your stylesheet if you wish to set the background.