[Deff]

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

<div class="alert">
    <button type="button" class="close" data-dismiss="alert">&times;</button>
    <span>Err1</span>
    <span>Err3</span>
    <span>Err2</span>
    <span>Err3</span>
    <span>Err2</span>
</div>

<script type="text/javascript">
var obj={};
$('div.alert > span:contains("Err")').each(function () {
  obj[$(this).html()]=$(this).remove();
});
for (var i in obj){
 $('div.alert').append((obj[i]))
};
</script>