jackbomb

In your theme folders, there’ll be a folder probably called CSS. In that folder, look for the file ‘screen.css’.

The main column is .span-16 {
width: 630px;

The sidebar is .span-8 {
width: 310px;

Bear in mind both of these lie within the container div, which is

.container {
margin: 0 auto;
width: 950px;

And within that, there’s a div…

.span-24, div.span-24 {
margin: 0;
width: 950px

So if you edit one, you’ll probably have to edit them all. But careful, because I suspect these will apply to stuff that you might not want to edit… not sure without going through it all….

Hope that helps?