I am not sure what property sets the redirect_uri url that appears in the popup facebook dialogue box when authenticating via facebook. I'm asking this because I would like to change it but all attempts have failed. Is this url set from the facebook app settings ( maybe from the site url) or does it need to be changed in JS?
if you use the Meteor accounts-facebook package, this URL is defined for you and is of the form: <your-site-url>/_oauth/facebook/?close
You need to set this URL in your Facebook App page under
Settings -> Advanced -> Client OAuth settings -> Valid OAuth redirect URIs