All ads are wrapped in the following tags:

<div class="advertisement" id="group-#"></div>

All ads are in the same "advertisement" class. Each ad group gets a unique id. This makes it possible to create generic advertisement formatting as well as specific advertisement formatting.

CSS Example 1:

This sample code can be added to your theme's custom style.css. It adds padding to advertisements, wrapping them in a dashed border and giving them a background color. It also adds the text "Advertisement:" above the ad:

.advertisement { padding: 5px; border: dashed; background-color: #ffd; }
.advertisement:before { content: "Advertisement:"; } 

CSS Example 2:

Here is more sample code that could be added to your theme's custom style.css. It will cause multiple image ads to be displayed horizontally one beside the other (space permitting), rather than vertically one below the other. The ads are aligned to the left side of the screen, if you'd prefer them to be aligned to the right side of the screen change the word "left" to "right" in the snippet:

.image-advertisement { float: left; padding: 3px; }