Your movie will need to be basically the right dimensions to begin with. If you have amovie which is 100 high and 500 wide it's never going to scale properly to fit the html window... however, in Flash use CTrl Shift F12 to edit the publish settings. In the HTML tab you can change the dimensions (use percantage, and 100% width and height) and the publish style. Changing the scale drop down will also allow you to make the flash movie scale to fit more exactly but it will disort the dimensions of your movie.
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