"I know how to do iFrame apps with PHP, but not Rails, not sure if that helps. The way you manage that is that you send it the same way to authenticate, but in the HREF to auth, remember to type "_top" to access the authentication flow through Facebook (not in the frame). When Facebook sends the user back to your app, you will be on the main index page. Sniff for the signed_request post object, and that will have a UID, noting that the user has authenticated. Koala has a flow for this, I just didn't do an example for that." - anna sauce