This tutorial will guide you to the process of integration of your web community with Facebook. This means that when a visitor comes to your site it can log in with normal credenditals if it has, but if it has not it can click on the facebook connect button and try to log in with its facebook account, automatically.
This is a good thing because, of course, your community is not so big and famous that every visitor wants to register and become a user to leave just a comment, but probably your visitors already have a Facebook account. So why loose their comments?<br/> More: you can use facebook connected users to post automatically on users facebook walls, that is to say, you can increase your traffic.
The target is to add facebook connect functionality with small changes to your code, we also want to make very small changes to your database and to your normal login process.
Here is the link of the tutorial: http://www.barattalo.it/facebook-connect-tutorial/