function popup_impressum() {
        var meinFenster=window.open("../impressum.php", "ImpressumPopUp", "menubar=no, location=no, resizable=no, width=425, height=275, left="+(screen.availWidth-425)/2+", top="+(screen.availHeight-275)/2+", alwaysRaised=yes, scrollbars=no");
}

function popup_rechnung(kunden_nr,renr) {
        var meinFenster=window.open("../rechnung.php?kunden_nr="+kunden_nr+"&renr="+renr+"", "RechnungPopUp", "menubar=yes, location=yes, resizable=yes, width="+screen.availWidth+", height="+screen.availHeight+", left=0, top=0, alwaysRaised=yes, scrollbars=yes, toolbar=yes, status=yes");
}