"random" effects

i see a lot of flash sites and the like with what appears to be random effects. a little light here and dot there...mostly data looking stuff...id like to put some of this into my site...i realize its just mc's im not asking about how to randomize stuff but i was wondering how one goes about making these mc's...theres so many different things happening at once how does one decide oh ill put this hear that there and activate that thing after this goes....? just trying to understand hte concepts of making this stuff

you basically answered your own question. As being a intermediate flash developer myself, you dont usually put alot of thinking into putting something "random" into your site intro or banner. Its random and you just kinda flop it wherever, with little insite to it, i mean dont put a circle out in the middle of your intro thats 100% opacity, because thats obviously not implemented well. But just randomly make a movie clip that as a dot that blinks, and randomly put it into your banner or intro....its really that simple. of course one could make it difficult...up to the designer