function toggleNav(elem){
	if(document.getElementById("nav_"+elem).style.display == "block")
		document.getElementById("nav_"+elem).style.display = "none";
	else{
		document.getElementById("nav_"+elem).style.display = "block";
		elem1 = (elem == "product")?"references":"product";
		document.getElementById("nav_"+elem1).style.display = "none";
	}
	//alert(document.getElementById("nav_"+elem).className);
}