Facebook had recently updated its chat module converting it into a sidebar that takes up the right hand corner on the Facebook page. The Facebook Chat Sidebar can be used not only for chatting but also sending offline messages, all these with a single click. If you do not like the new Facebook Chat Sidebar feature and want to revert back to the old chat style, you can do so by using browser extensions listed below. Interestingly Facebook has not given an option to switch between the new and the old chat system.
The new chat sidebar is good but then many still like the old Facebook chat box. The new Facebook sidebar can send offline messages, which as of now was missing in Facebook Chat module. Facebook could have made the chat sidebar better by at least adding an option to show only online friends. It really gets annoying to see the offline friends and you need to check for a green dot next to the name which indicates that the Facebook user is online.
The new Facebook Chat Sidebar feature is not enabled on most account so in case you still find the old chat style, relax, but sooner or later the new chat design may be implemented all over Facebook.
How to switch back to the good old Facebook chat and disable the new Facebook chat sidebar
Firefox users download the Sidebar disabler extension
Opera users download the Sidebar disabler extension
Chrome users download the Sidebar disabler extension
After downloading and installing the extension simply refresh the Facebook page and what you will get is the old Facebook chat. There is an option to switch back to the Facebook chat sidebar, in case you change your mind.