I'm working on a fade in and out script in JS on http://www.opssystems.co.uk/

Currently in the script below the $active keeps returning null and i'm unsure why as I am matching on the class active.

Any tips?

Thanks
Code JavaScript:
    function slideSwitch() {
        var $active = $('#slideshow a.active');
 
        if ( $active.length == 0 ) $active = $('#slideshow  a:last');
 
        // use this to pull the images in the order they appear in the markup
        var $next =  $active.next().length ? $active.next()
            : $('#slideshow a:first');
 
        // uncomment the 3 lines below to pull the images in random order
 
        // var $sibs  = $active.siblings();
        // 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}, 1000, function() {
                $active.removeClass('active last-active');
            });
    }
 
    $(function() {
        setInterval( "slideSwitch()", 5000 );
    });