wordpress theme customization (make column fixed)

It's for this website: [login to view URL] I need the comments column to remain in a fixed position, right now it will move according to the width of the window, if it is too narrow it will move under the featured image, it should stay the same width and fixed to the right of the image. This is a huge problem with smart phones, since the thumbnails aren't visible unless the user scrolls down. I need this to be done while disturbing the website as little as possible since people are browsing thru it now.