ciao, ho fatto come hai detto, ma non va completamente, puoi vedere come viene qui: esempio
con mozilla si vede in un modo e con ie in un altro

ecco il codice della pagina index:
Codice PHP:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<meta http-equiv="content-type" content="text/html; charset=iso-8859-1" />
<link href="bluebusiness.css" rel="stylesheet" type="text/css" />
<script src="mootools.js" type="text/javascript"></script>
<script type="text/javascript">

   window.addEvent('domready', function(){
  $$('#navigation li.Toogler').each(function(li){
     li.set('oldheight', li.getStyle('height').toInt());
     li.addEvents({
        'mouseenter' : function(){
           var ul = this.getElement('ul');
           if(ul){
               var height = this.getElement('ul').getSize().y + this.getStyle('height').toInt();
               this.tween("height", height);                           
           }
        },
        'mouseleave' : function(){
           this.tween('height', this.get('oldheight').toInt());
        }
     });
  });
});

</script>




</head>
<body>
<div id="container">
  <div id="container-header">
    <div id="container-name"><span>Blue</span>Business</div>
    <div id="container-slogan"><span>&quot;</span>your slogan goes here<span>&quot;</span></div>
  </div>
  <div id="container-eyecatcher">
    <div id="container-navigation">  
   <ul id="navigation">
      <li class="Toogler">[url="#"]home[/url]   
      <li class="Toogler">
         [url="#"]products[/url]
         <ul>[*][url="#"]Subproduct 1[/url]      [*][url="#"]Subproduct 2[/url][*][url="#"]Subproduct 3[/url][/list]
         
      <li class="Toogler">[url="#"]services[/url]   [/list]
</div>

    [img]images/business_eyecatcher.jpg[/img] </div>
  <div id="container-content">
    <div id="content">
     </div>
  </div>
  <div id="container-footer">
    <div id="footer">
      <div id="footer-copyright"></div>
      <div id="footer-meta"></div>
    </div>
  </div>
</div>

</body>
</html>