There is this thing on the bottom of firefox and I have no idea what it is or how to get rid of it. It makes it not worth using, I can't get to anything on the right side of the screen, and some things flash. I uninstalled and reinstalled firefox but it didn't go away. This is worded really awkwardly because I'm completely inept.
Here is a picture of it. What is it and how do I get rid of it?