If you can't get your website/web app to work with the FaceBook LogIn app ... here is the solution. First, this is the error you get when someone tries to login with Facebook:
Solution:
FB has recently updated things, and so you have to do the following when setting things up on https://developers.facebook.com/apps/:
Use Strict Mode for Redirect URIs" by default it is "Yes" and that's the problem. Need to be in "No"
See my attachment.
Stefan