To modify configuration stuff as hardware acceleration, etc... in firefox, put "about:config" in the url bar.
Also make sure that in tools/options/advanced "Use harware acceleration when available" is checked.
This should give you some leads for firefox.
For the ghost shooter, I believe it is the fullscreen options that eats FPS.
On my PC it runs at 11 FPS in FF6.
Modify, in the project properties of the ghostshooter.capx, the property "fullscreen in browser" to "no". 20 FPS announced, but the game feels more fluid to me.
Also FF is known to execute HTML5 slower than chrome and/or IE9.
Ninja'd by Rebirth