This page is very well written, and is just a little off. I have a couple of recommendations. First, within the Netscape portion of the branching logic in the showMenu() function (in the amenu.js file), the code is setting left and top values on a LAYER element, but within the page the dropdown menus are declared as DIV elements. So the values are not being updated on the dropdown menu.
One possible change for the Netscape 7.1 part of the script would be:
menuDiv = document.getElementById(theName);
menuDiv.style.left = Xpos;
menuDiv.style.top = Ypos;
This will work for any browser that implements the current W3C standards. For more info and a set of good examples, check out: http://devedge.netscape.com/viewsource/2001/updating-dhtml-web-pages/
The next thing I saw was the populating of the Left and Top coordinates. The showMenu() function is called before the clickHandler() event. This is accounted for in the script for IE versions of browsers, but not for Netscape 7.1.
Hopefully this helps.