Actually, picking the right proportions is more important than the exact dimensions you use. Flash has the unique ability to scale the contents of your entire Web page to fit any size browser window. As we discuss page size, we come to two different worlds of measurement. Flash measures page size in pixels by default, but FreeHand doesn't have that option. To make things easier, convert the measurement system in FreeHand to points, and from then on treat points as pixels.
Points are a fixed unit of measure, and the definition of a pixel can change.
But, for our purposes, it works fine. The ratio will be the same, and that's what matters the most. Even with Flash's ability to scale, it's probably a good idea to design your pages so that they'll look good on a 640 x 480 monitor. However, if you feel most of your visitors will be using screens at 832 x 624 or larger, you can design for that size. When you've decided on a page size, go to the Document Inspector, shown in Figure B, and select Custom from the pop-up menu.