[SOLVED] Formatting - Tag, Category, and Archive Pages

I asked this question in a slightly different way last week, and after messing around with the ideas Juggledad gave me, I'm still stumped. I know there's an easy answer to my question, so I'll re-ask it in a more broad sense. Is there any difference between the way a category/tag/archive page is rendered as opposed to how the index page is rendered as far as CSS formatting is concerned? To get a better idea of what I'm referring to, here's my site: Newdust.com

The one issue I'm trying to solve has to do with the blue striped background I've given the container of the top advertisement banner. This was achieved from a line of CSS I entered into Header.php. If you click on any of the tags listed to the left (click here for example), you'll notice that the blue stripe disappears. This is true also for category or archive pages. I would like the background of the advertisement's container to stay consistent no matter where the reader is within the site. Does anyone have any idea of what might be causing this to happen, and what could be done to fix it?