Tryit Editor v1.8

Source Code:

<!DOCTYPE html>
<html>
<head>
<script src="//ajax.googleapis.com/ajax/libs/jquery/1.10.1/jquery.min.js">
</script>
<script>
$(document).ready(function(){
  var x=0;
  $("p").click(function(event){
    $("p").animate({fontSize:"+=5px"});
    x++;
    if (x>=2)
      {
      $(this).unbind(event);
      }
  });
});
</script>
</head>
<body>

<p style="font-size:20px;">Click this p element to increase its size. The size can only be increased 2 times.</p>

</body>
</html>

Result:

W3Schools.com - Try it yourself

Edit the code above and click "Submit Code" to see the result.