DHTML « Actionscript Programming « Flash Tutorials

Now you're all done in your image editor, so fire up Flash MX. Once in Flash, import your newly created PNG file into your library and create your movie just as you would normally. You can add all the scripting, animation and interaction you want, just like you would a normal Flash movie. So how do you get it use the transparencies? Well, go into your publish settings and hit the HTML tab. Under "Window Mode" simply select "Transparent Windowless".