Resizing columns

Hallo folks,

My blog’s theme has two columns. The pages were narrower but I managed to widen the page and make it bigger. However, I would like to make the left column bigger than the right column but I dont know how to. If you look at
http://www.ecanhappen.com/wordpress you will see that there is a line which separates the columns. How can I move this line further to the right to make the left column bigger?

At the moment, it is looking a bit clumsy. I would like to move the line in the middle to the right but dont know where this can be changed. your help is much appreciated.