adjusting plugin css

I recently downloaded and installed this Plugin:

MDV Archive
Author: Nick Momrik
Version: 1.1
Author URI: http://mtdewvirus.com/

It works like a charm, I was just wondering how I would go about editing it to look nicer. Mine lookes like this:http://www.mrpkbb.com/blog/?cat=6

While the one on Nick’s website looks like this:
http://mtdewvirus.com/archives/

As you can see, mine leaves much to be desired.

I’m a total n00b, so if somebody has already asked this question or it is explained in another section please tell me.