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.backgroundColor = "#abcdef";
            }
            navItems[i].onmouseout=function() {
                this.getElementsByTagName('ul')[0].style.display="none";
                this.style.backgroundColor = "#FFFFFF";
            }
         }
      }
      
      if(navItems[i].className == "submenu2")
      {
         if(navItems[i].getElementsByTagName('ul')[0] != null)
         {
            navItems[i].onmouseover=function() {
                this.getElementsByTagName('ul')[0].style.display="block";
                this.style.backgroundColor = "#abcdef";
            }
            navItems[i].onmouseout=function() {
                this.getElementsByTagName('ul')[0].style.display="none";
                this.style.backgroundColor = "#FFF";
            }
         }
      }
   }
}