"Move fast and break things" is Mark's prime directive to his developers and team. "Unless you are breaking stuff," he says, "you are not moving fast enough."
Looks like Facebook has been fast in breaking things to the extent of breaking the chat box interface when they rolled out "something awesome" - Skype Video Calling and Group Chat, that is. Basically it's Skype on Facebook. So when they moved too fast, they ended up messing with chat box.
The New Facebook Chat Box Layout
This is how the new Facebook Chatbox layout looks like. You would have no idea as to the exact number of your friends are online and there's no way to scroll down or up. Also, it looks like my grouping doesn't work because it simply shows a limited view of a few friends online all at one view and I could not sort them in any way. It means I could no longer be offline to a specific group.
The Solution on How to Bring Back the Old Facebook Chat Box
The good news is that there's a get-around with it. If you're using Google Chrome or Mozilla Firefox as your internet browser then you can simply download a script or add-on, respectively.
Solution to Mozilla Firefox
Install this Firefox Facebook Sidebar Chat Reversion Greasemonkey add-on. Once you're done downloading it, simply restart your browser and you will be greeted with the old Facebook chat box.
Solution to Google Chrome
Google Chrome users don’t need to download Greasemonkey since the Chrome browser natively supports the extension so all you need to do is install the Chrome / Firefox Facebook Sidebar Chat Reversion user script.
Google Chrome also allows you to get back the old Facebook chat interface while in Incognito Mode. To do that, just tick the box that says “Allow in Incognito” under “Facebook Sidebar Chat Reversion” in Extensions (Settings > Tools > Extensions).
Facebook Chat Pop Out
If you wish not to install any Greasemonkey user script, you can always opt to use the Facebook Chat Pop Out.
There you have it, there are several ways to fix the new Facebook Chat Box and easily revert or bring it back to its old form. You simply need to choose which one is being supported by your browser or whichever you prefer. Happy chatting! :)