function slideSwitch(t) {
    var $active = $('#head img.active');

    if ($active.length == 0) $active = $('#head .ss:last');

    var $sibs = $active.siblings('.ss');
    var rndNum = Math.floor(Math.random() * $sibs.length);
    var $next = $($sibs[rndNum]);

    $active.addClass('last-active');

    $next.css({ opacity: 0.0 })
            .addClass('active')
            .animate({ opacity: 1.0 }, t, function () {
                $active.removeClass('active last-active');
            });
}

$(function () {
    slideSwitch(750);
    setInterval("slideSwitch(1250)", 4500);
});