you have to edit the template for the pop up in your style
dfh_announcement_popup
Code:
<DIV ID="ANNLAYER" STYLE="background-color: black; position: absolute; margin-left:255; margin-right:255; margin-top:354; margin-bottom:50; top: 341px; bottom: 120px; left: 130px; right: 5px; padding: 1px; overflow: auto; border-color: 000000; border-style: solid; border-top-width: 1px; border-right-width: 1px; border-bottom-width: 1px; border-left-width: 1px;">