3.html

<!DOCTYPE html>
<html>

<head>
  <meta http-equiv="Content-type" content="text/html; charset=utf-8">
  <title>hello-backbonejs</title>

  <script src="https://ajax.googleapis.com/ajax/libs/jquery/1.6.1/jquery.min.js" type="text/javascript" charset="utf-8"></script>
  <script src="http://ajax.cdnjs.com/ajax/libs/json2/20110223/json2.js" type="text/javascript" charset="utf-8"></script>
  <script src="http://ajax.cdnjs.com/ajax/libs/underscore.js/1.1.6/underscore-min.js" type="text/javascript" charset="utf-8"></script>
  <script src="http://ajax.cdnjs.com/ajax/libs/backbone.js/0.3.3/backbone-min.js" type="text/javascript" charset="utf-8"></script>
    
  <script src="3.js" type="text/javascript" charset="utf-8"></script>
</head>

<body>
</body>

</html>