The golden rule of Web site navigation is the two-click rule. Anything a visitor wants to see on your Web site needs to be available within two clicks of the home or start page.
Navigating a Web site is difficult without a simple, clear table of contents and clear page headings. Visitors need to know where they are, where they can go and how they can return to where they came from. If visitors hit a dead end or want to turn around, they'll quickly exit the site if there's no easy way back to the home page. With a table of contents in the margin on each page, they can proceed easily and directly to any other page on the site.
Excerpted from 101 Internet Marketing Tips For Your Business