For the most part, I don’t think this is completely a mystery anymore. Most people are starting to learn the importance of a sitemap. First, let me begin by explaining what is a sitemap.
A sitemap is exactly what the name states, a map of your web site. There are two tips of sitemaps, an HTML version that you would include in your links and an XML sitemap that you would submit to places like Google Webmaster Tools, Yahoo Site Explorer, or MSN’s Live Search Webmaster Tools.
The latter of these is not organized like an HTML sitemap, it simply contains all of the web pages your site has to offer. By creating an XML sitemap and submitting it to the three aforementioned places, it’s a great way to get all of your deep content indexed.
An HTML sitemap is quite similar in the sense that it should also include all of your links on your web site. The only difference is that it should be organized in a visual, useful fashion.