function on()
{
    document.getElementById("shadow").style.visibility = 'visible';
    $("#shadow").css("height", $(document).height()).show();
    document.getElementById("sehlis").style.visibility = 'visible';
}

function off()
{
    $("#shadow").css("height", $(document).height()).hide();
    document.getElementById("impressum").style.visibility = 'hidden';
    document.getElementById("close").style.visibility = 'hidden';
}