Facebook has finally added the ability to access the site via a HTTP
Secure (HTTPS)connection, which should drastically increase security
HTTPS provides a combination of the HTTP and SSL protocols, enabling
encrypted communication between your computer and a web server. Without
it you're exposed to sniffing attacks on the network; for example, if
you're using a public Wi-Fi to Access Facebook. via plain HTTP, someone using the Firesheep add-on for Firefox can easily retrieve your data. HTTPS makes it a lot harder to do that.
The feature is available as an option on the Account Setting page. If you don't see it yet, don't worry; Facebook will be gradually rolling it out over the next couple of weeks.
Those who are concerned about online security probably know that it was
possible to access Facebook via HTTPS for quite some time now, for
example using the HTTPS Everywhere Firefox add-on, but some of Facebook's features, for example chat and photo uploads, did not work properly over HTTPS.
Unfortunately, even Facebook's implementation of the protocol will not
be perfect. "Some Facebook features, including many third-party
applications, are not currently supported in HTTPS," writes Facebook's
Alex Rice in a Blog Post,
promising that Facebook is working hard to resolve these issues.
Furthermore, if you choose to enable HTTPS, you should know that it will
slow down your Facebook Experience , as encrypted pages take longer to load.
Source :- Yahoo News