It seems apparent that you are using a custom template based upon the default. The default template stylesheet.css is basically unrefined, a raw base, to learn about initial customizing. You'll notice in the stylesheet that there are Selectors missing and thus, the lack of symmetry between the right/left columns and so forth. The easiest recommendation is to download the Classic color combo pack;
http://www.zen-cart.com/index.php?ma...roducts_id=274

From there, you can pick the relative color scheme that you desire and you can begin customizing from a solid base. Or you can just compare stylesheets to complete your current default stylesheet.