Was using the facebook Force.com toolkit https://wiki.developerforce.com/page/Getting_Started_with_the_Force.com_Toolkit_for_Facebook,_Version_3.0. Followed all the instructions as mentioned in the link.
I installed the toolkit and also configured the settings (public site creation). I created a new facebook app as well. But after creating the app when I try to access the site. (As mentioned in the following sentence of the installation guide: Go to your site URL (e.g. https://fbtest-developer-edition.na14.force.com/) and you should be prompted to log in to your new app and authorize it to access your data)
I am blocked and the following error shows up.