One of the hardest things to do while multitasking is watching a video. Even if you open a clip in a new window, you often have to keep moving it around your screen so it's not blocked by all the clutter on your screen. Mozilla's new Picture-in-Picture feature for Firefox pins just about any video to your screen and prevents other tabs or windows from obscuring it.
Once you've downloaded the most recent version of Firefox, hover over a video and a blue "Picture-in-Picture" option will pop up. Click the button and the video will open in a solitary player that you can move around as needed. The feature is only available on the Windows version of the browser, but it will hit Mac and Linux versions in January, according to Mozilla.
While having a second monitor would probably be the nicest way to keep one eye on a video and the other on work tasks, that's not an option for everyone, and would be next to impossible for laptop users on the go. Picture-in-Picture mode could be a good fallback. Just make sure you've got a quick trigger finger for when your boss walks by.