[Deff]

Добавляем ID

<script src="http://code.jquery.com/jquery-latest.js"></script>

<div class = "wrapper">
 <div class = "inner"> 123 </div>
 <div class = "inner"> 123 </div>
 ..............
 <div class = "inner"> 123 </div>
 </div>

<script type="text/javascript">
$("div.wrapper > div.inner").each(function(i){
  $(this).attr('id','NewId_'+i);
});
alert($("div.wrapper").html());
</script>