This is a Firefox extension which disables the 0-9, Home and End 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 following keys are disabled by default, but can be optionally enabled in the addon settings:

• Top row 1-9
• Numpad 1-9
• 0
• Home
• End

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.