flash actionscript: theoretical question:
I have noticed that setInterval or onEnterFrame animations aren't so smooth when swf is embeded in browser,
why?

you either have a frame rate too low (when using onEnterFrame), setInterval()
with a frequency parameter too high, setInterval() with adquately low frequency
parameter but no updateAfterEvent(), animations too numerous or complex for the
host machine to handle smoothly or some other issue. but those are the most
common ones.