Making two sidebars independent of each other

URL: http://techtage.com/2013/07/8-important-things-in-a-post-penguin-link-building-world/

I don’t want the bottom sidebar to shrink when the right sidebar is used. I also want the right sidebar as a fixed unit, instead of a rather ‘floating’ unit.

I mean, if the right sidebar height is more than content height, the bottom sidebar should start after the end of the right sidebar.

Any clues?