sub-cat divs and product divs

Hi

Trying to figure out how to alter the size of divs on a category listing page without altering div size on a product listing page. It looks like the two are connected size wise. Saw something about altering thumbnail size in the frontend CSS but really I just need to change the size of the div. Anyone know where I could find this.

Site address...
kateaud.cloudaccess.net/vintage.html

Just looking to reduce the size of the divs on here so less white space

Thanks