I want to add the ability to 'login with Facebook' to my site. But I am confused when I register my site in Facebook Apps. What should I input into App Domains?
the app domain is your domain name.
Before you enter your domain, first click on Add Platform, select website, enter your site URL and mobile site url. Save the settings.
Thereafter, you can enter the domain name in the App domains field.
See more at my blog: http://www.ogbongeblog.com/2014/03/unable-to-add-app-domains-to-new.html