That depends. You can do Exact Fit in the scale drop down from Dreamweaver but this will distort the dimensions of your movie and I hate it.
I generally make my movies the right scalable dimensions for their environment. If they're going to run as standalones I use 640 x 480 and if they are going to run in a browser I make them about 300 x 500. This way they scale well within a maximized browser.
Please don't email or PM
me Flash questions, that's what the Forums are for!
Please don't rely on me reading my PMs either. Email me about important stuff.