function popup(url, title, W, H, features){
	var X = Math.ceil((window.screen.availWidth - W) / 2);
	var Y = Math.ceil((window.screen.availHeight - H) / 2);
	features = "width=" + W + ", height=" + H + ", left=" + X + ", top=" + Y + ", " + features;
	window.open(url, title, features);
}

function openCenterWindow(url, title, width, height) {
	var left = Math.ceil((window.screen.availWidth - width) / 2);
	var top  = Math.ceil((window.screen.availHeight - height) / 2);
	window.open(url, title, "menubar=no,status=no,scrollbars=yes,resizable=yes,width=" + width + ",height=" + (height + 30) + ",top=" + top + ",left=" + left);
}