// open a popup window, specifying source, width, and height, and optionally a name; if no name, choose a random one

	function popup(source, width, height, window_name) {
		if (! window_name) { 
			now = new Date();
			window_name = now.getTime();
		} else {
			window_name = window_name.replace(/ /g, "_");
		}
		popup_window = window.open(source, window_name, "width=" + String(width) + ",height=" + String(height) + ",location=no,menubar=no,directories=no,toolbar=no,scrollbars=yes,resizable=yes,status=yes");
		popup_window.focus();
		// return popup_window; // oops, this creates a weird behavior in Firefox and Win/IE
	}