I have decided to enable users that already have a Facebook account (who hasn’t ?!) to log on my site with their Facebook credentials. Process has shown to be pretty easy but It took me some time to figure out few things. I have decided to implement so called ‘Single Sign-On’ and I pretty much followed guildlines from http://developers.facebook.com/docs/guides/web. So, not to loose your precious time, let us start from the beginning.