In Publish Settings if you choose 100% x 100% that should create an HTML holder that will allow the movie to resize whilst maintaining the aspect ratio.

Always use an HTML container - don't link to the SWF directly as you may find you have problems.

Be careful about allowing resizing. I use a 1600x1200 display and a movie rarely runs as smoothly at that size as it will at 800x600 - the PC simply cannot cope unless you have a high-end graphics card fitted when there's a lot of animation full-screen.

The split is about 50:50 between most users having 800x600 and 1024x768 set on their PCs.

Therefore - and this is a personal opinion where others feel differently - design for 800x600 unless you have a specific reason not to (i.e. if you are doing a techie dweeb site then most users will have holographic, 100" displays. In their dreams, anyway :))

If you go for 800x600 allow for the viewable browser area and make your movie about 760x400 (that's what I use). Then it will fit without scrolling.

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Sualdam