.NET Modal Window Styling

I am using the ModalPopupExtender control provided by the current AJAX Control Toolkit installed in Visual Studio 2010 to generate modal popup windows for my web site using the code provided at the below link: [login to view URL] I have attempted to modify the CSS Style to make the modal popup windows appear like Facebook style modal windows, however, I have been unsuccessful. In particular I am looking for the transparent wide border, rounded edges and a white popup background (see attached files for samples).