noob question: Centering Stuff in CSS w/ Sidebars

I'm pretty new to CSS, and this has been throwing me for a loop. I want to make a layout where there are two sidebars, one on the left, one on the right, and the main content in the middle. How would one go about doing this?

Another problem I'm running into is that while the left sidebar is all the way at the top of the screen, the right sidebar is further down the page. I used float:left-down on the two blocks I wanted on the left, and that worked fine. I used float:right on the right block, if that helps.

 

What you want to do and more: http://layouts.ironmyers.com/

 

you might use element positioning instead of floats