A simple sitemap is an important tool to insure that every page of your site gets indexed.
A sitemap can be a manually coded page that lists all the pages of the site, or can be created via special tools such as www.xml-sitemaps.com
Once sitemaps are created and installed, their locations should be spelled out in a robots.txt file.
Here is information on creation of a robots.txt file which will assist search engine robots in indexing your site:
Each site should include a robots.txt which specifies sitemap locations.
To specify the location of sitemaps, just put a line like this anywhere in your robots.txt file:
Replace the Sitemap: http://www.yoursite.com/ with the actual full URL. For example, if www.yoursite.com has a sitemap file called sitemap.xml in top level, the reference would be like this:
If you have more than one sitemaps you can either create a special “sitemaps index” file that links to all of them, then put a link to the sitemaps index file in your robots.txt file.
An simpler process is to simply list more than one sitemaps in the robots.txt file.