Images that are part of the content <div> have an underline. How to remove this

["Jaap A. Haitsma" <jaap haitsma org>]

E.g. look at the GNOME buttons on
http://www.gnome.org/friends/thank-you.html
They have a dotted line under the images because the images link to
another page.

I can of course solve it on that page by putting these images in a
seperate <div> and set custom styling for the <a> links in that <div>,
but I think it would be better to solve it globally. Also the image on
http://www.gnome.org has a dotted line under the image

Jaap