This message occurs when you can access the NetCommunity website with multiple domain names.
For example, users can access the site using or

In order to resolve this, you must log into Google Webmaster tools and select a Preferred Domain for the site - this will be either or
Additionally, log into the NetCommunity site, and set the non-preferred domain as an alternate URL.  To do this:
1. Log in the NetCommunity website as an administrator
2. Click on Administration > Sites and Settings
3. Select the site you are working with from the tree on the left hand side
4. Add the non-preferred domain to the Alternate Site URL field.  

Users will still be able to access the site using wither URL, but they will be routed to the site via the preferred or main domain.