Help with Custom CSS

I’m using headway themes. And I came across a site that was pretty cool, it had two sidebars, side by side, that spanned the whole page vertically, overlapping the header etc. to the top. Another wrinkle, the top portion of it was blended/merged into one wider sidebar, while below it is two separate ones.

http://theclickstarter.com/

What kind of CSS would allow me to do something similar?