var popupWindow = null;

function closepopup() {
	if (popupWindow != null) {
		popupWindow.close();
	}
}

function popup() {
	closepopup();
	popupWindow = window.open('blank.html', 'popup_window', 'width=640,toolbar=no,location=yes,menubar=yes,directories=no,status=yes,scrollbars=yes,resizable=yes');
	popupWindow.focus();
}