How to implement a web page that scales when the browser window is resized?

Question

How to implement a web page that scales when the browser window is resized?

I can lay out the elements of the page using either a table or CSS float sections, but i

Answer 1

instead of using in css say "width: 200px", use stuff like "width: 50%"

This makes it use 50% of whatever it's in, so in the case of:

The div will now always take up half the window horizontaly.