Front end developers: stop moving things that I’m about to click on
A particular bane of mine is the self-oscillating UIs, youtube is particularly bad at it these days - if the mouse pointer is in 'just the right place' (which is bigger than it sounds) then you get the seek-bar preview frames popup, which moves things just enough that the mouse pointer is no longer over the area that triggers it, so it vanishes, and the whole thing starts again.