javasvcript not trigger

javasvcript not trigger

Using the selection on the left panel, I load the results on the right
panel using jQuery Ajax. So far it's working really good:


...
$.ajax({
   url: "includes/content.php",
   data: "letter=" + letter.substr(letter.lastIndexOf("=") + 1),




   success: function(data) {
      $('#wrapper').removeClass("loading");
      $('#content').html(data).fadeIn(400);
   }




});


...

After the results are loaded on the right panel, I click on an <a> tag (<a class="btn_play">Play</a> ) that is suppose to trigger some javascript but doesn't:

javasscript to trigger:
$('a[class=btn_play]').click(function(event) {
   event.preventDefault();



   // get the A tag ref
   var file = $(this).attr('href');


   alert(file);

});


The same <a> tag also exists on the left panel and triggers correctly.
But, on the right panel, it doesn't trigger at all! I believe it's
because it doesn't see the javascript.



I'm sure this is come out already, but i can't find the solution.

Any hints?

Thanks
Marco