The following resolved question appears to address the same problem, but the solution DOES NOT WORK! (for me): https://support.mozilla.org/en-US/questions/1113500 I am using a Logitech wireless keyboard/touchpad device. It emulates a scroll wheel with a two-finger gesture. When I use that ,there is some coasting, which is OK. However, if I hit the Control key to modify some other key I am about to hit (like w or f), any sitil-ongoing scrolling becomes unintended zooming. This happens to me frequently, and I only just figured out what was causing. (I had been blaming it on Logitech.) I don't use ctrl-scroll-wheel to zoom anyway. So I just want to disable it.