How to make my site increase size or shrink as per browser window size?

We are working on a website - http://wordpressboon.com/portercreek

Client want it that it should increase size or shrink in size as per screensize or browser window. No vertical or horizontal scrollbar should appear. See this sample- http://screencast.com/t/AeBLcyokW
or http://templatesden.com/TF/WPCMS/spasalon/

The above site is decreasing its size if you decrease your browser window size