Jquery applying class and removing class

Jquery applying class and removing class

The code which changes the active class to the currently clicked
pagination class. Removing it works but adding the new class doesn't work.
http://jsfiddle.net/spadez/qKyNL/35/
$('a').click(function(event){
event.preventDefault();
var number = $(this).attr('href');
$.ajax({
url: "/ajax_json_echo/",
type: "GET",
dataType: "json",
timeout: 5000,
beforeSend: function () {
$('#content').fadeTo(500, 0.5);
},
success: function (data, textStatus) {
// TO DO: Load in new content
$('html, body').animate({
scrollTop: '0px'
}, 300);
// TO DO: Change URL
$('#pagination li.active').removeClass("active");
$(this).parent().addClass("active");
},
error: function (x, t, m) {
if (t === "timeout") {
alert("Request timeout");
} else {
alert('Request error');
}
},
complete: function () {
$('#content').fadeTo(500, 1);
}
});
});
Can anyone please tell me where I am going wrong?