function checkInput()
{
if(document.Feedbackformular.Kundenemail.value == "" ||
   document.Feedbackformular.Feedback.value == ""
   )
        {
                document.getElementById("Submitbutton").disabled = true;     // Submit-Button ausblenden
        }
        else
        {
                document.getElementById("Submitbutton").disabled = false;    // Submit-Button einblenden
        }
}