Layout problems, navigation next/prev problems?

Hello,
I’m currently creating this website:
http://www.filvadro.com/

from the blank theme. It looks well, however, whenever you click the categories/archives such as:

http://filvadro.com/category/copyright-basics/

the layout gets ruined as opposed to:
http://filvadro.com/2012/11/08/qa-on-art-contests-and-artists-copyright/
Which are single posts.

I was thinking it may have something in the archive.php but there are no divs there I should edit. I’ve been stuck on this for three days so I didn’t know what to do.

Also there’s this problem of the navigation next/prev not appearing on the page. A little help please? 🙁