In Search Engine Optimisation sitemaps can make the difference between your site being crawled and your site not being crawled properly. Google, Yahoo and MSN have now come together to agree on a new sitemap standard that means your sitemaps don’t have to be hosted on the same host as your website.
The new method that can be used is to define were your sitemap is located using your robots.txt file and this is where the search engines will read your sitemap from.
This method will not affect you rankings in any way but it could make it easier for webmasters to manage their sitemaps if they own multiple hosts.
E.g.
If you own two websites called www.host1.com and www.host2.com and host your sitemaps on a 3rd host (www.host3.com) then in your robots file on host 1 and host 2 you would specify were the sitemap is located.
Sitemap: www.host3.com/host1sitemap.xml
And
Sitemap: www.host3.com/host2sitemap.xml
Gary
NSEO Programmer