jQuery.fn.fadeToggle = function(speed, easing, callback) {
    return this.animate({opacity: 'toggle'}, speed, easing, callback);
};

// attach the onclick event to each anchor tag with a class of "div-toggle"
$("a.div-toggle").click(function () {
    // fade-in/out the element with the id of "my-div"
    $("#my-div").fadeToggle();
    // return false to prevent the anchor tag from following the href rule
    return false;
});