// create custom animation algorithm for jQuery called "drop" 
$.easing.drop = function(x, t, b, c, d) {
    return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;
};

// loading animation
$.tools.overlay.addEffect("drop", function(css, done) {

    // use Overlay API to gain access to crucial elements
    var conf = this.getConf(),
       overlay = this.getOverlay();

    // determine initial position for the overlay
    if (conf.fixed) {
        css.position = 'fixed';
    } else {
        css.top += $(window).scrollTop();
        css.left += $(window).scrollLeft();
        css.position = 'absolute';
    }

    // position the overlay and show it
    overlay.css(css).show();

    // begin animating with our custom easing
    overlay.animate({ top: '+=55', opacity: 1, width: '+=20' }, 400, 'drop', done);

}, function(done) {
    this.getOverlay().animate({ top: '-=55', opacity: 0, width: '-=20' }, 300, 'drop', function() {
        $(this).hide();
        done.call();
    });
}
);

$("a[rel]").overlay({
    effect: 'drop',
    mask: '#789'
});

$(document).ready(function() {

    $("a[rel]").overlay({
        effect: 'drop',
        mask: '#789'
    });

});