The main benefit of a good site map is that the search engines can traverse a site in a timely and logical manner and so the user can figure out where they are. A sitemap is a page with a list of links to all the most important documents on the site and is linked to from every page. However, it’s always surprising to see how many websites are unable to implement a decent sitemap correctly. How hard can it possibly be?
Generally, a sitemap should have no more than 100 links and contain some really keyword targeted anchor text. You see, any more than about 100 links could serve in decreasing the importance of some of the more important page links on the site. Sitemaps are also effective in aiding in the crawlability of the site for the search engines. Anything a webmaster can do to facilitate the crawling process for a search engine, the better.
There is a lot of work that goes into implementing an effective sitemap. Once you think you have it ready to upload to the site, be sure it makes sense to the user and that, of course, all of the links are functional. It is imperative that if a webmaster wants any chance of a search engine indexing the entire site, a well designed sitemap is a critical first step.