function MenueFunktion(element){
 var zu = element + "_zu";
 var auf = element + "_auf";
 if(document.getElementById(element).style.display == "none"){
  document.getElementById(element).style.display = "block";
  document.getElementById(zu).style.display = "none";
  document.getElementById(auf).style.display = "inline";
 }
 else{
  document.getElementById(element).style.display = "none";
  document.getElementById(zu).style.display = "inline";
  document.getElementById(auf).style.display = "none";
 }
}

function BilderFenster(link){
 var eigenschaften = "width=1000,height=710,location=no,menubar=no,resizable=yes,scrollbars=no,status=no,toolbar=no";
 fenster = window.open(link, "BF", eigenschaften);
 fenster.focus();
}

function FormularCheck(){
 var n = document.kontakt.name.value;
 var f = document.kontakt.firma.value;
 var e = document.kontakt.email.value;
 var b = document.kontakt.betreff.value;
 var t = document.kontakt.text.value;
 if(n=="" || f=="" || e=="" || b=="" || t==""){
  document.getElementById("fehler").style.display = "block";
  return false;
 }
 else return true;
}