function openBild(datei, breite, hoehe) {
    b = breite > screen.availWidth ? screen.availWidth : (breite * 1.1);
    h = hoehe > screen.availHeight ? screen.availHeight : (hoehe * 1.1);
    x = (screen.availWidth - b) / 2;
    y = (screen.availHeight - h) / 2;
    window.open(datei, 'bildchen', 'depenent=yes,location=no,menubar=no,status=no,height=' + h + ',width=' + b + ',left=' + x + ',top=' + y);
}