How to make three columns theme using css?

Question

I was looking to turn two columns snowflat theme into three columns.

Main column remains in middle. We already have right sidebar widget.

Column-1. 25% + Column-2  50% + column-3  25%

Can anyone offer css code to make snowflat theme in 3 columns.

Someone asked this question before but there was not any clear answer.

http://question2answer.org/qa/55179/can-make-three-column-site-with-question2answer-application

Thanks for your help in advance.