A frame rate that's too slow makes the animation appear to stop and start; a frame rate that's too fast blurs the details of the animation. Choose a frame rate of 12 frames per second (fps) for the best results on the web. QuickTime and AVI movies are generally 12 fps, while the standard motion-picture rate is 24 fps.
The complexity of the animation and the speed of the computer on which the animation is being played affect the smoothness of the playback. Test your animations on a variety of machines to determine optimum frame rates.
Because you specify only one frame rate for the entire Flash movie, it is a good idea to set this rate before you begin creating animation. See Creating a new movie and setting its properties.