function linkauf(xx) {
    f = document.getElementById(xx);
    f.style.visibility = 'visible';
}

function linkzu(xx) {
    f = document.getElementById(xx);
    f.style.visibility = 'hidden';
}

function show_div(divname) {
    document.getElementById(divname).style.visibility = "visible";
}
function hide_div(divname) {
    document.getElementById(divname).style.visibility = "hidden";
}

function pruefen() {
    var f = document.forms['kontakt'];
    var email = f.email.value;
    var name = f.name.value;
    var vorname = f.vorname.value;
    var telefon = f.telefon.value;
    var art1 = f.art[0].checked;
    var art2 = f.art[1].checked;
    var art3 = f.art[2].checked;
    var rueckruf = f.rueckruf.checked;
    var ok = 'ja';

    if (email == '') {
        f.email.style.backgroundColor = "#DFEFA5";
        ok = 'nein';
    }
    if (name == '') {
        f.name.style.backgroundColor = "#DFEFA5";
        ok = 'nein';
    }
    if (vorname == '') {
        f.vorname.style.backgroundColor = "#DFEFA5";
        ok = 'nein';
    }
    if (art1 == false && art2 == false && art3 == false) {
        f.art[0].style.backgroundColor = "#DFEFA5";
        f.art[1].style.backgroundColor = "#DFEFA5";
        f.art[2].style.backgroundColor = "#DFEFA5";
        ok = 'nein';
    }
    if (rueckruf == '1') {
        if (telefon == '') {
            f.telefon.style.backgroundColor = "#DFEFA5";
            ok = 'nein';
        }
    }            

    if (ok == 'nein') {
        document.getElementById('meldung').style.Color = "red";
        document.getElementById('meldung').style.visibility = "visible";
    }
    else {
        f.submit();
        document.getElementById('meldung').style.visibility = "hidden";
    }
}