When I'm going through an online video tutorial, I have to write all of the code shown to really solidify the concepts. As a result I spend a lot of time pressing
CMD + TAB to toggle between the browser video and my Vim session. This method is inefficient.
Helium to the rescue. Helium is a floating browser window for OS X, with some nice features like transparency. Position it on top of your console session, watch the video, and hack away in realtime.
h/t Dorian KarterTweet