gistfile1.js

//This will alert the self HTML
$.getJSON("?callback=?http://twitter.com/followers/ids/" + username + ".json",
  function(data){
   alert(data);
  });

//This will alert the JSON data retrieved
$.getJSON("http://twitter.com/followers/ids/" + username + ".json?callback=?",
 function(data){
  alert(data);
});