Ubuntu Unity introduced new overlayed scrollbars. If you don’t like them you can remove them as follows.

Command line method

If you are happy using the command line and have sudo privileged, open a terminal window (Ctrl -Alt-T) and type

sudo apt-get remove overlay-scrollbar

You’ll be prompted for your password.  Some applications running may need to be restarted to use the default scrollbars.

Alternative using the Software center

If you don;t have sudo privilege or you prefer a to use the a GUI application.  Open the Ubuntu Software Centre (from launcher or click on the dash and type soft – the software center should appear in the list, click on it)

In the search bar on the top right enter “overlay”. At the botton of this window click on the Display ?? technical items” link. This will display several Scrollbar overlay entries.

Near the top of the list will be one called “Scrollbar Overlayed widget” with a package name of “overlay-scrollbar”. Select the Remove button.

Next find an one or more entry called “Scrollbar overlayed widget – shared lib”. Select the Remove button for each of these in turn.

With all these entries removed your scrollbars should revert to standard scrollbars.

If you have applications running you probably need to close and restart them for the change to take effect. Some applications may require a system restart to make the standard scrollbars available.