Make a new user account and see if the problem follows you to the new account.
If it's just Firefox, try Chrome and if only in Firefox, reset Firefox after you backup your favorites (how to reset and backup is on the web.)
I have an old Dell 1540 laptop 32/64 bit, using Firefox browser. The screen/window consistently is 'bouncing' up and down. It will not obey my mouse demands either-i scroll up-window drops down and vica versa. Im using a windows wireless mouse,
This problem is driving me nuts! Takes all the pleasure out of using it.
Any answers will be much appreciated.