here are many SEO tips and tricks that help in optimizing a site but one of those, the importance of which is sometimes underestimated is sitemaps. Sitemaps, as the name implies, are just a map of your site - i.e. on one single page you show the structure of your site, its sections, the links between them, etc. Sitemaps make navigating your site easier and having an updated sitemap on your site is good both for your users and for search engines. Sitemaps are an important way of communication with search engines. While in robots.txt you tell search engines which parts of your site to exclude from indexing, in your site map you tell search engines where you'd like them to go.
Sitemaps are not a novelty. They have always been part of best Web design practices but with the adoption of sitemaps by search engines, now they become even more important. However, it is necessary to make a clarification that if you are interested in sitemaps mainly from a SEO point of view, you can't go on with the conventional sitemap only (though currently Yahoo! and MSN still keep to the standard html format). For instance, Google Sitemaps uses a special (XML) format that is different from the ordinary html sitemap for human visitors.
One might ask why two sitemaps are necessary. The answer is obvious - one is for humans, the other is for spiders (for now mainly Googlebot but it is reasonable to expect that other crawlers will join the club shortly). In that relation it is necessary to clarify that having two sitemaps is not regarded as duplicate content. In 'Introduction to Sitemaps', Google explicitly states that using a sitemap will never lead to penalty for your site.
Why Use a Sitemap
Using sitemaps has many benefits, not only easier navigation and better visibility by search engines. Sitemaps offer the opportunity to inform search engines immediately about any changes on your site. Of course, you cannot expect that search engines will rush right away to index your changed pages but certainly the changes will be indexed faster, compared to when you don't have a sitemap.
Also, when you have a sitemap and submit it to the search engines, you rely less on external links that will bring search engines to your site. Sitemaps can even help with messy internal links - for instance if you by accident have broken internal links or orphaned pages that cannot be reached in other way (though there is no doubt that it is much better to fix your errors than rely on a sitemap).
If your site is new, or if you have a significant number of new (or recently updated pages), then using a sitemap can be vital to your success. Although you can still go without a sitemap, it is likely that soon sitemaps will become the standard way of submitting a site to search engines. Though it is certain that spiders will continue to index the Web and sitemaps will not make the standard crawling procedures obsolete, it is logical to say that the importance of sitemaps will continue to increase.
Sitemaps also help in classifying your site content, though search engines are by no means obliged to classify a page as belonging to a particular category or as matching a particular keyword only because you have told them so.
