Fade in the active ID content in Ajax

<script type="text/javascript">

$(document).ready(function() {

    //When page loads...
    $(".tab_content").hide(); //Hide all content
    $("ul.tabs li:first").addClass("active").show(); //Activate first tab
    $(".tab_content:first").show(); //Show first tab content

    //On Click Event
    $("ul.tabs li").click(function() {

        $("ul.tabs li").removeClass("active"); //Remove any "active" class
        $(this).addClass("active"); //Add "active" class to selected tab
        $(".tab_content").hide(); //Hide all tab content

        var activeTab = $(this).find("a").attr("href"); //Find the href attribute value to identify the active tab + content

        if($(activeTab).html() == '') {
          $.ajax({
            url: '/url/to/post',
            type: 'post',
            dataType: 'html',
            success: function(content) {
              $(activeTab).html(content);
            }
          });
        }

        $(activeTab).fadeIn(); //Fade in the active ID content
        return false;
    });

});

</script>