Space bar is hilarious for me on YouTube/Firefox. Some times it gets into a certain focus state (play button focussed?) and hitting space bar will briefly pause it, then resume playback. Hilarity ensues as I scramble, pausing a few times to realize the issue, and change the focus to something else by clicking the video canvas then press spacebar again for success.
This hits something that I've come across before. Web pages are actually 3D with focus, always. But it's not clear, because the representation is 2D and the focus is either limited to certain elements (like ) or has to be manually implemented by the developer. And sometimes, like with YouTube, even long lived websites with supposedly lots of experience get it wrong.
And this is hard to think about as a developer, imagine how it is for someone non-internet native, who barely understand the mouse-abstraction we all gotten so used to.
I do think touchscreens have made technology possible for a lot of groups who didn't understand it before. Maybe we need something similar for desktop and laptop to avoid 3D in 2D jam we're in now.