How to add icons to top navigation menu?

How can i add icons to a menu item in the top navigation menu? I filled in an icon, but i see nothing. Also in Firefox no sign of an icon or :before tag...

What do i need to do? 

Icons in the top navigation menu are not working. There is a bug in dolphin somewhere.

I submitted a ticket on the problem months ago. http://www.boonex.com/trac/dolphin/ticket/3308 Seems the problem has existed since the release of dolphin 7.1

An idea how i can do it manually?