Centering Images on Category Pages

Hey,

I'm having trouble trying to center the images on my category/product listing pages.

This is what the code looks like in my main stylesheet:

#categoryImgListing {}
.categoryImg{ float:left; padding:0; border:1px solid #eaeaea; width:100px; height:100px; overflow:hidden;}
.categoryImg img{ width:100px; height:100px;}

I've tried doing a bunch of things already but nothing has taken effect.

Am I looking in the right place?

Thanks!

please submit a url to the page in question please ...

Here's an example: http://dumoresuppliesonline.com/index.php?main_page=index&cPath=3

Some of the category pages look good, like this one: http://dumoresuppliesonline.com/index.php?main_page=index&cPath=32 but the other ones are really ugly!

Thanks!

Still trying to figure this out... it's driving me nuts! Help would be greatly appreciated!!! :)