function mainTab(obj) {
	if(!document.getElementsByTagName) return false;
	if(!document.getElementById) return false;
	if(!document.getElementById("nk")) return false;
	if(!document.getElementById("nn")) return false;

	document.getElementById("nk").style.display="none";
	document.getElementById("nn").style.display="none";

	document.getElementById(obj).style.display="block";
}

function mainTabLoad() {
	if(!document.getElementsByTagName) return false;
	if(!document.getElementById) return false;
	if(!document.getElementById("nn")) return false;

	document.getElementById("nn").style.display="none";
}

addLoadEvent(mainTabLoad);