Bottom Margin on Whats New Product Boxes

[wotnow]

Hi .. my webdeveloper toolbar says that the element in the Whats New LH Sidebox .. ie the 3 product boxes inside the WhatsNew Sidebox are .sideBoxContent centeredContent .. so I made the following code in my CSS and added a green background but it makes no difference.

.sideBoxContent centeredContent {
padding:3em 0 3em 0;
background-color:#090;}

I am trying to add some bottom margin to separate them from each other.
Site is:
http://www.rosedakinjewellery.com.au...products_id=20

Thanks