Ever clicked a hint link in an exercise problem statement or a link to a related article on a screencast page and wished the link had opened in a new tab/window (rather than navigating within the current tab)? Well, that's how exercise pages and screencast pages work now.
It might seem like a small change (and it is) but it's hopefully a handy one. No more accidentally navigating away from pages in the middle of writing code or in the middle of watching a screencast.