var source;
  var getElemDetail = document.getElementById('detail');
  var getElemImgDetail = document.getElementById('imgDetail');
  var getElemOverview = document.getElementById('imgOverview');
  var arrImg = new Array();
  function imgChange(source) {
    if (source == 'zurück') {
      getElemImgDetail.style.display = 'none';
      getElemOverview.style.display = 'block';
      divShow('imgOverview');
      for (var i=0; i < arrImg.length; i++) {
        document.getElementById(i).className = 'on';
      }
      
    } else if (source == 'weiter') {
    
      source = getElemDetail.src;
      
      if (getElemImgDetail.style.display == 'none') {
        getElemOverview.style.display = 'none';
        divHide('imgOverview');
        getElemDetail.src = source;
        document.getElementById(0).className = 'off';
        getElemImgDetail.style.display = 'block';
      } else {
        source = source.split("bilder/");
        source = source[1];  
      
        for (var i=0; i < arrImg.length; i++) {
          if ((source == arrImg[i]) && (source != arrImg[arrImg.length-1])) {
            getElemDetail.src = 'img/bilder/' + arrImg[i+1];
            document.getElementById(i+1).className = 'off';
            if (i != arrImg.length-1) {
              document.getElementById(i).className = 'on';
            }
          } else if ((source == arrImg[i]) && (source == arrImg[arrImg.length-1])) {
            getElemDetail.src = 'img/bilder/' + arrImg[0];
            document.getElementById(0).className = 'off';
            if (i != 0) {
              document.getElementById(i).className = 'on';
            }
          } 
        }
      }
      
    } else {
    
      getElemDetail.src = 'img/bilder/' + source;
      getElemImgDetail.style.display = 'block';
      getElemOverview.style.display = 'none';
      divHide('imgOverview');
      for (var k=0; k < arrImg.length; k++) {
        if ((source == arrImg[k])){
          document.getElementById(k).className = 'off';
        } else {
          document.getElementById(k).className = 'on';
        }
      }
    }
  }