Theme Customization (Floating content area)

I am more a designer than a coder and pretty new to Wordpress,
How can I get this effect added to a theme, where the content area floats above the header.
Also the shadow area added to the content area separating it from sidebar area.
If someone could direct me to a site that explains this and gives code examples it would be much appreciated.
What is the correct terminology for such effects so I can "Google" them.

Thanks JIM