[Resolved] CSS causing faint horizontal line at bottom of table

Our website was originally developed using Kompozer. We are redoing it in WordPress. Kompozer appears to have used tables for layout. One feature of old site was highlighting certain paragraphs in gray. Previously I asked about how to apply a CSS style, and you suggested simply using a div tag and class name, using Text editor. That has worked fine. Thank you.

But now getting ready for launch of new site we notice a thin horizontal line and extra space at the bottom of each of these highlighted gray areas. I looked at the HTML and can’t see where the horizontal line and space comes from. I presume that comes from CSS somewhere. How can I change this to get rid of the horizontal line?

Example: Coal page. Old site: https://thinkglobalgreen.org/COAL.html
New site: http://pow.qqp.mybluehost.me/coal/

First gray box is for December 2015 item.