Full Screen Flash rules

I need a little help when designing something in flash for a full screen view.

I designed a flash swf file at 1024 X 680 when I full screen it it look a little distorted in on my screen of 1440. Why is that. What are the rules of designing something so that anyone from 1024 above can view it as I designed it?

I see some sites that look good in any screen resolution how is this done. What should I size my flash stage to fit any size? above 1024, should I be designing it bigger than 1024? for my stage and graphics? Thanks