body or #wrapper.

It is probably best to use a wrapper element and not the body as a wrapper. This is because it will make your life as the developer easier to control and manipulate elements and sections in your layout. You should use the wrapper to contain most elements in your html to make sure you have proper alignment for all of your information. Furthermore you should also use sections within your wrapper as well. Sections will help you distinguish and group information and elements within the wrapper. So for instance you can have a header, navigation, content, and footer sections. To go a little deeper with each section you can also make even more distinguishing parts to your layout. For instance in your content section you can make a left column, middle column, and right column. All of this the wrapper element, sections, and columns provide the same service for the layout and that is to section off elements for the purpose of information flow and aesthetics.