Can't do Facebook integration

I fill in the "App Domains" field for my site's Facebook app and click save, but it returns the following message:

App Domains: [] should not contain protocol information.

How to solve this? Thanks.
^ I tried that as well, but then I just got another kind of error:

You have specified an App Domain but have not specified a valid integration URL. must be derived from one of: Site URL, Mobile Site URL, Canvas URL, Secure Canvas URL, Page Tab URL or Secure Page Tab URL.