function dropdown() { 

   var navItems = document.getElementById("empresa").getElementsByTagName("li");
   for (var i=0; i< navItems.length; i++) {
      if(navItems[i].className == "submenu")
      {
      if(navItems[i].getElementsByTagName('ul')[0] != null)
         {
            navItems[i].onmouseover=function() {this.getElementsByTagName('ul')[0].style.display="block";this.style.backgroundColor = "#f9f9f9";}
            navItems[i].onmouseout=function() {this.getElementsByTagName('ul')[0].style.display="none";this.style.backgroundColor = "#FFFFFF";}
         }
		 
      }
   }
}