function slideshow() 
{
    var $active = $('.banner div.active');

    if ( $active.length == 0 ) $active = $('.banner div:last');

    var $next =  $active.next().length ? $active.next() : $('.banner div:first');
    $active.removeClass('active')
    $active.addClass('last-active');
    
    $next.css({opacity: 0.0})
        .addClass('active')
        .animate({opacity: 1.0}, 1000, function() {
            $active.removeClass('active last-active');
        });
}

$(function() {
    setInterval( "slideshow()", 12000 );
});