function doReserveren(strTaal) {
 		var w = 800, h = 600;
 		if (document.all || document.layers) {
  			w = screen.availWidth;
  	   		h = screen.availHeight;
 	 	}
 		var popW = 600, popH = 600;
  		var leftPos = (w-popW)/2, topPos = (h-popH)/2;
  		window.open("reserveren_" + strTaal + ".asp","reserveren","width="+popW+",height="+popH+",top="+topPos+",left="+leftPos+",scrollbars=no");
}