how to restore the old version of Facebook chat and it worked. And believe it or not, it's pretty much fast and simple. It literally took me seconds to do the whole process (using Chrome). All you need to do is to install a small add-on and/or script depending on your browser (i.e. Firefox, Chrome, Safari, etc.). Restart your browser and presto! - Facebook chat old version restored!
Check out my Facebook homepage now:

How to restore Facebook chat old version?Here are the steps:
For Google Chrome (This is said to be the recommended method. If you don't have Chrome yet, you can download it here: http://www.google.com/chrome)
1. Just install this script: http://userscripts.org/scripts/source/107159.user.js
2. Restart the browser and enjoy chatting.
For Mozilla Firefox
1. Install this add-on: https://addons.mozilla.org/en-US/firefox/addon/greasemonkey/
2. Install this script: http://userscripts.org/scripts/source/107159.user.js
3. Restart your browser. You can now enjoy the old Facebook chat version.
For Safari
1. Install this add-on: http://www.mactalk.com.au/18/56726-how-install-greasemonkey-scripts-safari.html2.Install this script: http://userscripts.org/scripts/source/107159.user.js
3. Restart your browser.
Credit to Otaii ...