Those are warnings that we really can't do anything about. The XML namespaces we define are the ones for your Open Graph objects used within your Application, and that's required for some of the Facebook features to integrate properly. Unfortunately, Facebook expects a very specific HTML doc type of RDFa, which is rarely actually used on real websites. Most websites (really, the templates) use the XHTML spec in the Doctype definition.
With all that jargon out of the way, what it really boils down to is that HTML validation doesn't really matter much, in general. Facebook requires certain things to be set how they are. Google has stated that improper HTML has no effect on search engine rankings. All browsers are able to work around the oddities that each of the 'big' networks impose (weird xmlns tags from Facebook, etc) and render the page just fine.
Obviously, if you are experiencing any real-world issues that you think are from JFBConnect, we'll gladly help resolve them. We've done a lot to make our code as validation-compliant as possible, but there's some things we simply can't work around.
I hope that helps explain,
Alex
Validation errors
