function validateForm()
{
    if(document.getElementById("vorname").value == "" || document.getElementById("name").value == "" || document.getElementById("email").value == "")
    {
       alert("Bitte folgende Felder ausfüllen:\nVorname, Name und E-Mail");
       return false;
    }
    return true;
}

function popup(file)
{
   helpwindow = window.open(file,"Kontaktformular","width=380,height=474");
   helpwindow.focus();
   return false;
}