Recently now when I go to Facebook, and I have a notification that says "Joe Schmoe has commented on your Site." When I click that notification, it now sends me to an error page. I can still find that comment if I go directly to the Site.
Doing a little snooping, the Error page tells me that I haven't set my Canvas URL. Where/how do I get that? It's not in the setup process of the Facebook Comments Plugin.