Sitemap and robots.txt
If you use a “Sitemap” file in order to give the map of your website to search engines, you don't have to manually tell to each search site the sitemap file URL. You have an easier way: you just have to add into your “robots.txt” file the following line:
The next time a search crawler will read your “robots.txt” file, it will automatically know how to get your website “Sitemap” file.
Search engine supporting “Sitemap” files are Google, MSN and Yahoo.