Internal linking raises your PR.
Even more important than having the proper keyword density is correctly linking your pages internally. It's probably the most overlooked aspect of good SEO.
You can have every page in your site link back to a single page and raise its PR just from the links you created. It's certainly better than nothing. A large part of SEO is naming your anchor links and using them internally. You'll notice throughout this site that we link to certain pages of our own. This is both to help you navigate our site, and also to help the search engines by showing them which pages are important to us.
Think about this SEO strategy from an e-commerce point-of-view. Would you rather have a high-ranking terms of service page or a high-ranking sales page? I know which one I'd prefer!
We're writing this crash course in internal linking strategy to make sure that every page on your site passes PR back to your home page. This can be done by simply adding an anchor text link to the footer of your web site (look, we did it here).
You can also link every page on your site from a site map
if you have "orphan" pages that need to be spidered by the engines but aren't included in your menu. A site map is a basic page that has a hyperlink
for every page that you want the search engines to find.