productListing - vertical spacing

How do I add a little space between the items in a productListing? Specifically, when I go to a category with multiple products, the image for each product touches the next image (vertically). I tried adding a productListing-odd (and even) class with margin on the top and bottom, but that didn't do anything.

THANKS!

.productListing-odd td, .productListing-even td {
text-align: left;
vertical-align: top;
padding:0.5em;
margin-bottom: 1em;
border-bottom: 3px double #aaccbb; /adjust to taste/

add the above to your stylesheet.css

Aha - I forgot the "td" when I tried it.

And THANKS for the other tweaks, the left-justification, top-align and bottom border all look great!!