Follow up: http://forum.bytesforall.com/showthread.php?t=15200

Arch, now I want the buttons also Transperant, see what happens: http://www.dharma-net.nl/ The menu buttons have a white background color, how do I get that Transperant ?

The background image is working great now

Is there a way the set the hight (in pixels or mm or pt) of the menu bar? now it scales to the FONT size and I cannot use a solid line anymore

Firebug to the rescue (along with some experience in using it).
This will get you a transparent menu.

div#menu1 ul.rMenu li {
    background: transparent !important;
}

You could add a height to that as well but you will have to fiddle with the CSS to get the text where you want.

Thats true but now this:

div#menu1 {
background-image: url("http://www.dharma-net.nl/images/dharma_menu_back.jpg");
}

is not working anymore

Now I have:

div#menu1 ul.rMenu {
background: transparent;
}

div#menu1 {
background-image: url("http://www.url.ex/images/image.jpg");
}

But the buttons are NOT transparent, the Menu is!

The menus are the most complex CSS on the site - there is over 400 lines of CSS governing the menus.

You need to consider the 'pseudo' settings of the links (a:active , a:hover) as well. As Larry said, you should get familiar with FireBug in FireFox you can play and see what needs to be changed

Ok, clear! THX!