FindOverflowClass(document.childNodes, 'frag')

function FindOverflowClass(nodes, clName)
{
  var i;
  
  for(i=0; i<nodes.length; i++)
  {
    if(nodes[i].className && nodes[i].className == clName)
    {
      AssignOverflowClass(nodes[i])
    }
    FindOverflowClass(nodes[i].childNodes, clName);
  }
}

function AssignOverflowClass(el)
{
  if(el.scrollHeight > el.clientHeight)
  {
    el.parentNode.className += ' overflow';
  }
  else
  {
    el.parentNode.className = el.parentNode.className.replace(/\s*overflow/,'');
  }
}