Flash 9 timing inaccuracies
Normally, when you’re developing a typical game (PC or console), you want to let the game as fast as it can, and write the gameplay and update routines so that they can compensate for arbitrary frame timings. In the Flash world, however, it is desirable sometimes to have the movie run at a fixed FPS, and have your game logic assume that arbitrary frame rate. If the movie should slow down for some reason, so will your logic, but at least things will be deterministic and stable.
Unfortunately, just because your movie is set to run at, say, 30 fps, doesn’t mean your browser will run it at that frame rate. My current application runs at a solid 30fps in the standalone Flash 9 player, but only manages an anemic 22 fps when viewed in a page via Firefox. IE isn’t much better, and only clocks in at around 24fps. What’s going on? I turned practically everything in the application off (including all graphics), and there was no change in framerate!