function openWindow(url, target, width, height) {
	if (url != '') {
		width = (width) ? width : 640;
		height = (height) ? height : 480;

		var leftPos = (screen.availWidth - width) / 2;
		var topPos = (screen.availHeight - height) / 2; 
		var opts = "toolbar=no,status=no,location=no,menubar=no,resizable=yes,";
		    opts += "width=" + width + ",height=" + height + ",scrollbars=no,";
		    opts += "top=" + topPos + ",left=" + leftPos;
		var dialog = window.open("", target, opts);
		dialog.location = url;
		dialog.focus();
	}
	return false;
}