Kottke shares a Marginal Revolution link discussing various techniques for surviving an unplanned temporal displacement back to the Middle Ages, and the discussion is both funny and fascinating.
I have no idea what I’d do, as I’m relatively certain that CSS prowess (both HTML and First Person Shooter) wouldn’t translate very well. I’d probably opt for Bard status (Chaotic Neutral, of course) and kick-start the rock n’ roll revolution (or at least the singer-songwriter one). And then die as a witch.
No matter what, I’m pretty sure that your RenFest experience won’t work in your favor.