To fix this problem, you should select a preferred domain for your site. This means that you should decide which way you would like URLs from your site to be indexed.
The preferred domain is the one that you would liked used to index your site's pages (sometimes this is referred to as the canonical domain). Links may point to your site using both the www and non-www versions of the URL (for instance, http://www.example.com and http://example.com). The preferred domain is the version that you want used for your site in the search results.
Once you tell us your preferred domain name, we use that information for all future crawls of your site and indexing refreshes. For instance, if you specify your preferred domain as http://www.example.com and we find a link to your site that is formatted as http://example.com, we follow that link as http://www.example.com instead. In addition, we'll take your preference into account when displaying the URLs. If you don't specify a preferred domain, we may treat the www and non-www versions of the domain as separate references to separate pages.
If you would like the URLs from your site to be indexed without the www prefix, delete the Sitemap from your Google Webmaster Tools account and resubmit it using the path without the www prefix (for instance, http://example.com/sitemap.xml). If you use this option, you don't need to modify the URLs inside your Sitemap.
If you would like the URLs from your site to be indexed with the www prefix, you should modify your Sitemap to include www in the URLs listed there, then upload and resubmit your updated Sitemap.
This topic was started on Mar 31, 2011 and has been closed due to inactivity. If you want to discuss this topic further, please create a new forum topic.