var bilder = new Array(
'001','002','003','004','005','006','007','008','009','010','011','012','013','014','015','016','017','018','019','020','021','022','023','024','025','026','027');

function toprot()
{
var no= Math.round(Math.random()*(bilder.length-1));
document.write('<img src="back'+bilder[no]+'.jpg" width="650" height="140" border="0">');
}



function Bildwechsel (Bildnr, Bildobjekt) {
  window.document.images[Bildnr].src = Bildobjekt.src;
}