<script type="text/javascript">       
  divWeHave = document.getElementsByTagName('DIV');       
  replacement = new Array (       
  'Первая замена',       
  'вторая',       
  'третья и т.д.'       
  );       

  numer = 0;       

  for(i=0;i<divWeHave.length;i++){       
  if(divWeHave[i].className == 'forumModer'){       
  divWeHave[i].innerHTML = replacement[numer]+divWeHave[i].innerHTML.slice(16);       
  numer++;       
  }       
  }       
  </script>