HELP with ajax method - callback function not executed

HELP with ajax method - callback function not executed

hello all!

      i am trying to retrieve json data from the world bank's API, here's my code:

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

<script type="text/javascript">
var theData;
$(document).ready(function(){
  $("button").click(function(){  

$.ajax({ url: 'http://api.worldbank.org/sources?format=json', 
             success: function(data) {
                  /*this alert message does not show*/
                  alert(data);
             }, 
             dataType: 'json' 
            });
  });
});


</script>
</head>
<body>
<p></p>
<button> Get World Bank Data </button>
</body>

the callback function is not executed but there is response when i checked it using firebug.
i cant figure out what's wrong here. please help.