One of the most often asked questions I see on webmaster forums is about Google Sitemaps. In short, a Google Sitemap is a mechanism that allows Google to index your site with more accuracy. If you do not implement a Google Sitemap, Google will still index your site. So why should you setup a Google Sitemap?
Managing Google’s Bot
The main dilema is that you want Google’s bots to visit your site and index as much as possible, but after that you only need Google to index new content and not just waste bandwidth indexing previous content. The robots.txt file offers only limited options, it can’t tell bots to index only new content, so Google came up with Sitemaps to help webmasters make bots work more efficiently. Google’s Sitemap format makes it easy to tell the search engine bot, what your urls are, when they were last changed, and the frequency with which they change. This way the bot knows what it needs to look at and what it can ignore. This should help reduce crawling and make for more accurate indexing as well.
For websites that use non-engine friendly urls or sites that are brand new and have put a lot of content, the benefits of using a sitemap is that indexing will be more accurate. If your site is new and has no pagerank, a sitemap will not add your site any quicker than if you did not use a sitemap. The idea is not immediate search engine rankings, the idea is to have correct indexing, so when Google does add your site officially to its databases, all of your pages will be included correctly.
If you use WordPress, Google Sitemap Generator is a WordPress plugin that can create and manage your Google Sitemap. You can also create your own manually, just reference the Google’s Sitemap protocol.