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<div class="wrap">...</div>

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<script type="text/javascript">
// <![CDATA[
function einblenden (obj)
{
   obj.onclick = function (e) { ausblenden(this); };
   obj.firstChild.data = 'Ausblenden';
   obj.previousSibling.style.display = 'block';
}
function ausblenden (obj)
{
   obj.onclick = function (e) { einblenden(this); };
   obj.firstChild.data = 'Einblenden';
   obj.previousSibling.style.display = 'none';
}
window.onload = function (e) {
   var divs = document.getElementsByTagName('div');
   for ( var i = 0; i < divs.length; i++ ) {
      var div = divs[i];
      if ( div.className == 'wrap' ) {
         var btn = document.createElement('button');
         btn.appendChild( document.createTextNode('...') );
         div.parentNode.insertBefore( btn, div.nextSibling );
         ausblenden(btn);
      }
   }
};
// ]]>
</script>

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         btn.className = 'blender';