I recently wrote a Flash game using strictly ActionScript 3.0 in Flex Builder
3. The one thing I notice was even though I targeted 30 frames per second I
would only get ~24 fps when running in the browser. I stumbled across an odd
solution -- setting wmode in the embed tag to either transparent or opaque gets
the frame rate up to where it should be. Here is a simple example.

http://chrislongo.net/wmode/

Use the select to change between modes. On my machine under Firefox, window
mode runs around 24 fps where transparent and opaque run at 30 fps. I cannot
explain why and it's driving me crazy! From all I have read transparent and
opaque modes are supposed to *decrease* performance.

Any suggestions? The code for this example is very simple and I don't suspect
it's anything I am doing vs some sort of quirk with the Flash platform I am not
aware of.