liHover = function()
{
	var liEls = document.getElementById("main_nav").getElementsByTagName("li");
	for (var i=0; i<liEls.length; i++)
	{
		liEls[i].onmouseover = function()
		{
			this.className += " lihover";
		}
		liEls[i].onmouseout = function()
		{
			this.className = this.className.replace(new RegExp(" lihover\\b"), "");
		}
	}
}
if (window.attachEvent) window.attachEvent("onload", liHover);