You can create a complex design by combining different background properties, which is why we included the "area background" properties (including the central, main content, header, and footer area backgrounds) as well as related properties (e.g. central area margin and padding, etc.). These areas usually extend beyond the content area. Try experimenting with these settings to see what kinds of interesting effects you can create.
For more information about adjusting these settings, check out the Shopping Cart Designer Pro Help manual.