function slideSwitch() {
    var jQueryactive = jQuery('#testshow p.active');

    if ( jQueryactive.length == 0 ) jQueryactive = jQuery('#testshow p:last');

    var jQuerynext =  jQueryactive.next().length ? jQueryactive.next()
        : jQuery('#testshow p:first');

    jQueryactive.addClass('last-active');

    jQuerynext.css({opacity: 0.0})
        .addClass('active')
        .animate({opacity: 1.0}, 1000, function() {
            jQueryactive.removeClass('active last-active');
        });
}

jQuery(function() {
    setInterval( "slideSwitch()", 5000 );
});