I need to create an area of the page that has it\'s own scroll bar, just like the Facebook messenger in the image below.
Stack overflow has the same system at the an
This should help: http://manos.malihu.gr/tuts/jquery_custom_scrollbar.html
Another one here: http://dotroe.com/subpage.html
Those are jquery plugins that you can use on your pages.
Use j scroll pane. It's great, very customisable, lots of demos here: http://jscrollpane.kelvinluck.com/#examples
I imagine that custom scrollbar is implemented in javascript, it looks very slick and you can't make a browsers scrollbar look that good!
Find an example I just put together for you at: http://jsfiddle.net/9LHPW/2/ - note check the resources tab as this includes four external files (3x Js and 1x CSS)
Have a look at this website for a further example (looks like exactly what you want) with Javascript and jQuery: http://manos.malihu.gr/tuts/jquery_custom_scrollbar.html
You can find the plugin's home at http://manos.malihu.gr/jquery-custom-content-scroller
Along with a how to use it section!