Overlapping elements - how to make dropdown menu on top?

I have drop down menus that are falling behind some pop up hover text boxes I have, and I would like to have the menus stay on top:

http://www.inkart.net/

(if you choose, 'Birds' from the top menu, then 'Songbirds' and the hover text box pops up.)

Here's the CSS: http://www.inkart.net/styles_20.css

Would like to keep the pop up box if possible, but behind the menus. Any suggestions on how to do this would be appreciated.

 

inkart.net/css3menu1/style.css

add:
ul#css3menu1{
position:relative;
z-index:10;
}