function slideSwitch() {
   var $active = $('#slider a.active');
   if ( $active.length == 0 ) $active = $('#slider a:last');
   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()",4500 );
});