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 = "#F2F2F2";}
                navItems[i].onmouseout=function() {this.getElementsByTagName('ul')[0].style.display="none";this.style.backgroundColor = "#F2F2F2";}
            }
        }
    }
}