history.pushstate fails browser back and forward button

Question

I'm using jQuery to dynamically load content in a div container.

The server side code detects if the request is AJAX or GET.

I want the browsers back/forward buttons to work with the code so I try to use history.pushState. I've got to following piece of code:

$('.ajax').on('click', function(e) {
    e.preventDefault();
    $this = $(this);
    $('#ajaxContent').fadeOut(function() {
        $('.pageLoad').show();
        $('#ajaxContent').html('');
        $('#ajaxContent').load($this.attr('href'), function() {
            window.history.pushState(null,"", $this.attr('href'));
            $('.pageLoad').hide();
            $('#ajaxContent').fadeIn();
        });
    });
});

Everything works fine except when browsing with the browsers back/forward button, the adress in the bar changes according to plan but the page doesn't change. What am I doing wrong?

Updated script with the help from Clayton's answer

var fnLoadPage = function(url) {
    $('#ajaxContent').fadeOut(function() {
        $('.pageLoad').show();
        $('#ajaxContent').html('').load(url, function() {
            $('.pageLoad').hide();
            $('#ajaxContent').fadeIn();
        });
     });
};

window.onpopstate = function(e) {
     fnLoadPage.call(undefined, document.location.href);
};

$(document).on('click', '.ajax', function(e) {
    $this = $(this);
    e.preventDefault();
    window.history.pushState({state: new Date().getTime()}, '', $this.attr('href'));
    fnLoadPage.call(undefined, $this.attr('href'));
});

Answer 1

@Barry_127, see if this will work for you: http://jsfiddle.net/SX4Qh/

$(document).ready(function(){
    window.onpopstate =  function(event) {
        alert('popstate fired');
        $('#ajaxContent').fadeOut(function() {
            $('.pageLoad').show();
            $('#ajaxContent').html('')
                             .load($(this).attr('href'), function() {
                                $('.pageLoad').hide();
                                $('#ajaxContent').fadeIn();
                             });
        });
    };

    $('.ajax').on('click', function(event) {
        event.preventDefault();
        alert('pushstate fired');
        window.history.pushState({state:'new'},'', $(this).attr('href'));
    });

 });

If you take a look at the fiddle I provided and click the button, the alert will fire showing that you are pushing a new state. If you then proceed to click the back button once the pushstate has fired, you will see that the previous page (or popstate) will fire.