If you’re like me, you probably find it terribly annoying when an annotation appears automatically over a YouTube video. They stick around until you dismiss them and block the view.
It’s possible to disable them for all videos by default, though. You need to be logged into your Google account (since it’s an account preference), once there, it’s an option under Playback Setup:
Uncheck “Always show captions” and “Show annotations” to keep them from popping up. You can re-enable them on a per-video basis by clicking the button along the bottom of the viewer.