Hola, este es el codigo, con explorer si funciona pero con mozilla no aparece el desplegable.
<script language="javascript">
var capa
ns4 = (document.layers)? true:false
ie4 = (document.all)? true:false
var ns6 = (document.getElementById && !document.all) ? true: false
var coorX, coorY
function init() {
if (ns4) {capa = document.menu}
if (ie4) {capa = menu.style}}
function mostrar(obj) {
if (ns4) obj.visibility = "show"
else if (ie4) obj.visibility = "visible"
else
document.getElementById(capa).style.visibility = "visible"}
function ocultar(obj) {
if (ns4) obj.visibility = "hide"
else if (ie4) obj.visibility = "hidden"
else
document.getElementById(capa).style.visibility = "hidden"}
</script>
</HEAD>
<BODY scroll="no" onLoad="theclock(),init()">
<table width="100%" height="100%" border="0" cellpadding="2" cellspacing="2">
<tr valign="top">
<th width="120" align="left" class="leftMain" scope="col">
<table width="100%" height="100%" border="0" cellpadding="0" cellspacing="0">
<tr>
<th height="200" align="left" valign="top" scope="col">
<table width="100%" height="100%" border="0" cellspacing="1" cellpadding="3">
<tr><th height="50" colspan="2" align="left" valign="middle" class="forMenu2" scope="col"><a href="index.html"><img src="images/title.jpg" width="103" height="35" border="0"></a></th> </tr>
<tr><th height="10"></th></tr>
<tr><th height="25" colspan="2" align="left" valign="middle" class="forMenu" scope="col">
<div id="CapaNormal" OnMousedown="mostrar(capa)"><a href="#">MRTG</a></div>
<div id="menu" style= "position:absolute;left:132; top:82; background-color:#cccccc; visibility:hidden" onmouseup ="ocultar(capa)">
<table class="formenu2" cellpadding="5">
