The archive.php page

Hello, if I’m correct I thought that the archive.php page handles both the archives and categories. When I click on the the previous issues link (which is my archives) the page looks fine, but when I click on the archives link the page is messed up as though the css isn’t translating. So I’m trying to figure out why it would be fine on one and not the other if the one css file points to the archive page?

here’s the site: http://halfmanhalfmachine.net/wordpress/

click on The blog in the nav menu at the top and in the sidebar your see Categories and Previous Issues.

Thank you for your help : )