Use the normal body tag to define background and links colors. If you are dealing with lots of products, you have to have a database site in order to manage things. For a basic catalog, these services could work. For sophisticated functionality, custom programming is usually required. A limitation of a database site is that search engines don't index dynamically generated pages.
Some database software creates html pages from the database pages.
ShopSite is one program that does this. This is a newish programming language that very well may replace HTML a few years out. Navigation links on the top of the page. All link bars were once on the side of the page. In the quest for more screen real estate for content, designers are moving navigation buttons to the top of the page.