Whole browser window question

ok, quick question and sorry if this has been asked before but I did look and couldn’t find it…

http://www.blackpulp.com/html/index.html
http://www.inhabitedtheband.com/v2/html/index_content.html

2 brilliant sites I really like and other than that share something else in common, they both fill the browser window. Looking at the source they both have their width and height set to 100%

I have a ton of questions on this (so when I said quick I maybe lying) but let me start with a couple of obvious ones.

When creating in Flash, what size do you set the movie at?
How do you scale anything?
How can this work in different resolutions and how can you be sure that nothing will be cut off?

…thanks for any info :cool: