Border on product-listing in column

[raimond]

I want to put a border on the product-listing with using 2 products in a column.

I added this code in my stylesheet.css

.centerBoxContentsProducts {
	border: 1px solid #9a9a9a;
	margin: 1px;
	}

In Internet Explorer it works okay with 3 columns. But not with two columns, when I do this, the products are listed under eachother.

In FireFox they both doesn't work. I got a strange format with 2 or columns.

How can I solve this that I can give a border on the product-listing for two columns in a row and also works fine on IE and FireFox?