function slideSwitch() {
var $active = $('#slideshow  IMG.active');
if ( $active.length == 0 ) $active = $('#slideshow IMG:last');

/* per andare in ordine*/
var $next =  $active.next().length ? $active.next() : $('#slideshow IMG:first');

/*  per andare random 
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()", 2000 );
});