function show () {
	for (i = 0; i < arguments.length; i++) {
		var e = document.getElementById(arguments[i]); 
		if (e) e.style.display = "";
	}
}

function hide () {
	for (i = 0; i < arguments.length; i++) {
		var e = document.getElementById(arguments[i]); 
		if (e) e.style.display = "none";
	}
}

function open_login_window () {
	offset = 0;
	offset = window.pageYOffset||document.body.scrollTop||document.documentElement.scrollTop;	
	document.getElementById('cover').style.top = offset + 'px';
	document.getElementById('loginpopup').style.top = 200 + offset + 'px';
    show("cover", "loginpopup");
    return;
}