function menuPrincipal() {

   var navItems = document.getElementById("menuSup").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.getElementsByTagName('a')[0].style.background="url('imagens/bgMenuhover.png')"}
            navItems[i].onmouseout=function() {this.getElementsByTagName('ul')[0].style.display="none"; this.getElementsByTagName('a')[0].style.background="none"}


         }
      }
   }

}