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