I've installed a wordpress-based directory and am trying to style the sidebar widgets. The default style of all widgets in the sidebar is enclosed in a border with a title text and background. However, I wish to remove all these styling when I'm inserting an image in the widget.

To see what I mean, you can go to this website. On the right hand sidebar, the first image "Add Listing Here" is enclosed in a border. How do I remove the styling for this image?

Any suggestion? Many thanks in advance.