function oeffnefenster (url) {
     fenster = window.open(url, "fenster1", "width=640,height=550,status=yes,scrollbars=yes,resizable=yes");
     fenster.focus();
}
function oeffnefenster2 (url) {
     fenster = window.open(url, "fenster2", "width=640,height=550,status=yes,scrollbars=yes,resizable=yes");
     fenster.focus();
}