When building websites, there are two types of navigation you need to keep in mind.  Navigation for humans and navigation for search engines.  In order to keep your site both human and search engine friendly, all websites should have both an HTML sitemap as well as an XML sitemap.

The XML sitemap is probably the most talked about nowadays with Google’s new Webmaster Tools.  The XML sitemap is used to give search engines a guideline as to how to crawl your website.  It can be submitted to Google, Yahoo, MSN, and other search engines in order to help them spider your website.  These XML sitemaps are becoming more and more common on the internet… if you do not have one, it will really give you a disadvantage.  If you cannot program and/or know nothing about XML, there are many free programs which can create XML sitemaps for you.  You can check out this site or my personal favorite  (a wordpress plugin).

HTML sitemaps have been more or less forgotten about… but they are even more important than XML sitemaps!  Not only can they help your visitors find content on your site, they also serve as a natural way for search engines to find your content.
If you are noticing some pages not being indexed by google, it is because Google cannot find them… throw up a simple HTML sitemap pointing to every page on your site and Google will find pages you didn’t even know you had!

One of my websites, www.funlol.com, is 8 years old.  Over those 8 years, it has built up over 10,000 pages of content.  Because 10,000 pages of content is very hard to keep track of, lots of my pages were getting lost and de-indexed by Google.  In order to combat this, I created a simple HTML sitemap listing all my items by date.  I found that since doing this, my pages are now being indexed by google every two days… compared to the 2 weeks that took before!