function horizontal() {
  var navItems = document.getElementById("menu_dropdown").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.color ="#fff500";}
         navItems[i].onmouseout=function() {this.getElementsByTagName('ul')[0].style.display="none";this.style.color="#FFFFFF";}
      }
    }
  }
}