var currentWidth = "";

function laenger(Balken) {
 currentWidth = Balken.style.width;
 var Breite = Balken.style.width;
 if (isNaN(Breite)) {
  Breite = parseInt(Breite);
 }
 neueBreite = Breite + 200;
 Balken.style.width = neueBreite;
 document.getElementById('Produktmenue').style.visibility = 'hidden';
}

function kuerzer(Balken) {
 Balken.style.width = currentWidth;
 document.getElementById('Produktmenue').style.visibility = 'visible';
}