This typically occurs on sites where individual users can have their own subdomain. For example on blogspot.com users can request their own personal sub-domain like myblog.blogspot.com.

When you then check myblog.blogspot.com on the appliance, you may see a categorization of "Personal Sites" and "Web Hosting". However, the same URL, when reviewed on sitereview.bluecoat.com, returns a result of "None".
 

This is due to a slight difference in how categorization on the appliance and on site-review works:

Site-review takes the exact URL and checks it against BCWF. If it's not contained in the BCWF database, we'll try to perform real-time rating (DRTR) by accessing the site and analyzing the content to determine the category. If that is not possible (maybe the index page only contains images or there is simply not enough content) then we will return a category of "None".

On the appliances, on the other hand, we would return the category of the parent domain, so in this case "Personal Sites" and "Web Hosting".