This is a Firefox extension which disables the 0-9 keyboard shortcuts on
YouTube, which seek to a percentage of the video, i.e. the 0 key seeks the
beginning of the video, the 1 key seeks to 10%, etc.
The volume control keys on my laptop are directly above the numbers:
Sometimes when I change the volume I accidentally press a number key which seeks to a different place in the video I am watching and causes me to lose my place. I have never used the number shortcuts to seek to a point in a video on purpose, so the easy solution is to disable the number keyboard shortcuts.