I can't seem to access one of the lessons in a tutorial, even though I already completed it. What should I do?

Due to the strange and magical forces of the interwebs and the way web browsers work, on rare occasions a tutorial may not be able to load a lesson you’ve already completed (we think it has to do with some weird caching issues…or inadequate virginal sacrifices to the IT gods, but we’re not sure). At any rate, the problem can usually be resolved by logging out of the website (save your work on the tutorial first, if necessary), and then logging back in and starting the tutorial again. If that doesn’t work, let us know and we’ll help resolve the problem.