var Slides = ["w1","w2","w3","w4"]; 
var wait = 500;  
var it=0;

function start_slideshow() {

setInterval('SlideShow()', 6000);  

}


function SlideShow() {

Effect.Fade(Slides[it], { duration:3, from:1.0, to:0.0 });
it++;

if (it == 4) it = 0;
Effect.Appear(Slides[it], { duration:2, from:0.0, to:1.0 });
}