Ubuntu 12.04 LTS Precise Pangolin), but you can test it on Ubuntu 11.10 Oneiric Ocelot.
Overlay Scrollbars are scroll bars with scrubbers that appear when passing your mouse cursor over the the program's scroll bar area. This new version will improve the overlay scrollbars usage, but this time it will appear across the height of the window.
Overlay Scrollbars Installation
Open the terminal and run these commands to install Overlay Scrollbars on Ubuntu 11.10:
sudo apt-add-repository ppa:ayatana-scrollbar-team/release
sudo apt-get update
sudo apt-get upgrade
Removing Overlay Scrollbars
If you want to disable overlay scrollbars completely, open the terminal and run this command:
sudo apt-get remove overlay-scrollbar liboverlay-scrollbar