Editing webcomic CSS

I am putting together a web comic. The website is based on a WordPress theme, Comicpress. I have edited the code with CSS so that the post is on the right side of the comic. My problem is that the right side-posts doesn’t stay fixed next to the comic. it will float when the browser is too wide and jump down when the browser is too narrow. I want it to stay put.

Can anyone tell me what I’m doing wrong? Should I be doing something with the php files instead of the CSS?
http://www.workshedstudio.com/test-blog/

(FYI: The picture files on the site are only fpo’s and the page is still a work in progress.)