Consulta sobre código script menú estilo windows

[Balterra]

He encontrado este script para crear en mi web un menú superior al estilo del de windows por defecto.

La cuestión es que en Firefox funciona perfectamente, cada sub-menú aparece anidado al lado del menú padre, pero en IE, cada nuevo sub-menú aparece en la parte superior izquierda, lo que hace bastante molesta la navegación.

Os copio el código (menús los enlaces de menú, que es HTML sin más). Espero que podáis ayudadme.

Código:

<style type="text/css">

div.menuBar,
div.menuBar a.menuButton,
div.menu,
div.menu a.menuItem {
  font-family: "MS Sans Serif", Arial, sans-serif;
  font-size: 8pt;
  font-style: normal;
  font-weight: normal;
  color: #000000;
}

div.menuBar {
  background-color: #d0d0d0;
  border: 2px solid;
  border-color: #f0f0f0 #909090 #909090 #f0f0f0;
  padding: 4px 2px 4px 2px;
  text-align: left;
}

div.menuBar a.menuButton {
  background-color: transparent;
  border: 1px solid #d0d0d0;
  color: #000000;
  cursor: default;
  left: 0px;
  margin: 1px;
  padding: 2px 6px 2px 6px;
  position: relative;
  text-decoration: none;
  top: 0px;
  z-index: 100;
}

div.menuBar a.menuButton:hover {
	background-color: transparent;
	border-color: #f0f0f0 #909090 #909090 #f0f0f0;
	color: #000000;
}

div.menuBar a.menuButtonActive,
div.menuBar a.menuButtonActive:hover {
  background-color: #a0a0a0;
  border-color: #909090 #f0f0f0 #f0f0f0 #909090;
  color: #ffffff;
  left: 1px;
  top: 1px;
}

div.menu {
  background-color: #d0d0d0;
  border: 2px solid;
  border-color: #f0f0f0 #909090 #909090 #f0f0f0;
  left: 0px;
  padding: 0px 1px 1px 0px;
  position: absolute;
  top: 0px;
  visibility: hidden;
  z-index: 101;
}

div.menu a.menuItem {
  color: #000000;
  cursor: default;
  display: block;
  padding: 3px 1em;
  text-decoration: none;
  white-space: nowrap;
}

div.menu a.menuItem:hover, div.menu a.menuItemHighlight {
  background-color: #000080;
  color: #ffffff;
}

div.menu a.menuItem span.menuItemText {}

div.menu a.menuItem span.menuItemArrow {
  margin-right: -.75em;
}

div.menu div.menuItemSep {
  border-top: 1px solid #909090;
  border-bottom: 1px solid #f0f0f0;
  margin: 4px 2px;
}

</style>

<script type="text/javascript">

function Browser() {
  var ua, s, i;
  this.isIE    = false;  
  this.isNS    = false;  
  this.version = null;

  ua = navigator.userAgent;

  s = "MSIE";
  if ((i = ua.indexOf(s)) >= 0) {
    this.isIE = true;
    this.version = parseFloat(ua.substr(i + s.length));
    return;
  }

  s = "Netscape6/";
  if ((i = ua.indexOf(s)) >= 0) {
    this.isNS = true;
    this.version = parseFloat(ua.substr(i + s.length));
    return;
  }

  // Treat any other "Gecko" browser as NS 6.1.

  s = "Gecko";
  if ((i = ua.indexOf(s)) >= 0) {
    this.isNS = true;
    this.version = 6.1;
    return;
  }
}

var browser = new Browser();

//----------------------------------------------------------------------------
// Code for handling the menu bar and active button.
//----------------------------------------------------------------------------

var activeButton = null;

// Capture mouse clicks on the page so any active button can be
// deactivated.

if (browser.isIE)
  document.onmousedown = pageMousedown;
else
  document.addEventListener("mousedown", pageMousedown, true);

function pageMousedown(event) {
  var el;
  if (activeButton == null)
    return;

  if (browser.isIE)
    el = window.event.srcElement;
  else
    el = (event.target.tagName ? event.target : event.target.parentNode);

  if (el == activeButton)
    return;

  if (getContainerWith(el, "DIV", "menu") == null) {
    resetButton(activeButton);
    activeButton = null;
  }
}

function buttonClick(event, menuId) {
  var button;

  if (browser.isIE)
    button = window.event.srcElement;
  else
    button = event.currentTarget;

  button.blur();

  if (button.menu == null) {
    button.menu = document.getElementById(menuId);
    menuInit(button.menu);
  }

  if (activeButton != null)
    resetButton(activeButton);

  if (button != activeButton) {
    depressButton(button);
    activeButton = button;
  }
  else
    activeButton = null;

  return false;
}

function buttonMouseover(event, menuId) {
  var button;

  if (browser.isIE)
    button = window.event.srcElement;
  else
    button = event.currentTarget;

  if (activeButton != null && activeButton != button)
    buttonClick(event, menuId);
}

function depressButton(button) {
  var x, y;

  button.className += " menuButtonActive";

  x = getPageOffsetLeft(button);
  y = getPageOffsetTop(button) + button.offsetHeight;

  if (browser.isIE) {
    x += button.offsetParent.clientLeft;
    y += button.offsetParent.clientTop;
  }

  button.menu.style.left = x + "px";
  button.menu.style.top  = y + "px";
  button.menu.style.visibility = "visible";
}

function resetButton(button) {
  removeClassName(button, "menuButtonActive");

  if (button.menu != null) {
    closeSubMenu(button.menu);
    button.menu.style.visibility = "hidden";
  }
}


function menuMouseover(event) {
  var menu;
  if (browser.isIE)
    menu = getContainerWith(window.event.srcElement, "DIV", "menu");
  else
    menu = event.currentTarget;

  if (menu.activeItem != null)
    closeSubMenu(menu);
}

function menuItemMouseover(event, menuId) {
  var item, menu, x, y;
  if (browser.isIE)
    item = getContainerWith(window.event.srcElement, "A", "menuItem");
  else
    item = event.currentTarget;
  menu = getContainerWith(item, "DIV", "menu");

  if (menu.activeItem != null)
    closeSubMenu(menu);
  menu.activeItem = item;

  item.className += " menuItemHighlight";

  if (item.subMenu == null) {
    item.subMenu = document.getElementById(menuId);
    menuInit(item.subMenu);
  }

  x = getPageOffsetLeft(item) + item.offsetWidth;
  y = getPageOffsetTop(item);

  var maxX, maxY;

  if (browser.isNS) {
    maxX = window.scrollX + window.innerWidth;
    maxY = window.scrollY + window.innerHeight;
  }
  if (browser.isIE && browser.version < 6) {
    maxX = document.body.scrollLeft + document.body.clientWidth;
    maxY = document.body.scrollTop  + document.body.clientHeight;
  }
  if (browser.isIE && browser.version >= 6) {
    maxX = document.documentElement.scrollLeft + document.documentElement.clientWidth;
    maxY = document.documentElement.scrollTop  + document.documentElement.clientHeight;
  }
  maxX -= item.subMenu.offsetWidth;
  maxY -= item.subMenu.offsetHeight;

  if (x > maxX)
    x = Math.max(0, x - item.offsetWidth - item.subMenu.offsetWidth
      + (menu.offsetWidth - item.offsetWidth));
  y = Math.max(0, Math.min(y, maxY));

  item.subMenu.style.left = x + "px";
  item.subMenu.style.top  = y + "px";
  item.subMenu.style.visibility = "visible";

  if (browser.isIE)
    window.event.cancelBubble = true;
  else
    event.stopPropagation();
}

function closeSubMenu(menu) {
  if (menu == null || menu.activeItem == null)
    return;

  if (menu.activeItem.subMenu != null) {
    closeSubMenu(menu.activeItem.subMenu);
    menu.activeItem.subMenu.style.visibility = "hidden";
    menu.activeItem.subMenu = null;
  }
  removeClassName(menu.activeItem, "menuItemHighlight");
  menu.activeItem = null;
}

function menuInit(menu) {
  var itemList, spanList
  var textEl, arrowEl;
  var itemWidth;
  var w, dw;
  var i, j;

  if (browser.isIE) {
    menu.style.lineHeight = "2.5ex";
    spanList = menu.getElementsByTagName("SPAN");
    for (i = 0; i < spanList.length; i++)
      if (hasClassName(spanList[i], "menuItemArrow")) {
        spanList[i].style.fontFamily = "Webdings";
        spanList[i].firstChild.nodeValue = "4";
      }
  }

  itemList = menu.getElementsByTagName("A");
  if (itemList.length > 0)
    itemWidth = itemList[0].offsetWidth;
  else
    return;

  for (i = 0; i < itemList.length; i++) {
    spanList = itemList[i].getElementsByTagName("SPAN")
    textEl  = null
    arrowEl = null;
    for (j = 0; j < spanList.length; j++) {
      if (hasClassName(spanList[j], "menuItemText"))
        textEl = spanList[j];
      if (hasClassName(spanList[j], "menuItemArrow"))
        arrowEl = spanList[j];
    }
    if (textEl != null && arrowEl != null)
      textEl.style.paddingRight = (itemWidth 
        - (textEl.offsetWidth + arrowEl.offsetWidth)) + "px";
  }

  if (browser.isIE) {
    w = itemList[0].offsetWidth;
    itemList[0].style.width = w + "px";
    dw = itemList[0].offsetWidth - w;
    w -= dw;
    itemList[0].style.width = w + "px";
  }
}

function getContainerWith(node, tagName, className) {
  while (node != null) {
    if (node.tagName != null && node.tagName == tagName &&
        hasClassName(node, className))
      return node;
    node = node.parentNode;
  }

  return node;
}

function hasClassName(el, name) {
  var i, list;
  list = el.className.split(" ");
  for (i = 0; i < list.length; i++)
    if (list[i] == name)
      return true;

  return false;
}

function removeClassName(el, name) {
  var i, curList, newList;
  if (el.className == null)
    return;
  newList = new Array();
  curList = el.className.split(" ");
  for (i = 0; i < curList.length; i++)
    if (curList[i] != name)
      newList.push(curList[i]);
  el.className = newList.join(" ");
}

function getPageOffsetLeft(el) {
  var x;
  x = el.offsetLeft;
  if (el.offsetParent != null)
    x += getPageOffsetLeft(el.offsetParent);

  return x;
}

function getPageOffsetTop(el) {
  var y;
  y = el.offsetTop;
  if (el.offsetParent != null)
    y += getPageOffsetTop(el.offsetParent);

  return y;
}

</script>

Saludos y gracias,

Balterra