If you use the Linux screen utility a lot for long running jobs etc you may have experienced scrolling issues. The quickest way is to try Control-a and then Escape. You should now be able to use Up/Down keys or even PgUp/PgDn. Press Escape to exit scrolling.
In my case most of the time the terminal is running in a Virtualbox guest so you may or may not have to take into account Virtualbox key grabbing/assigning.