var slide = 1;
var slides = 3;

function nextSlide() {
    var lastSlide = slide;
    slide++;
    if (slide > slides) {
        slide = 1;
    }
    $('#slider_'+slide).fadeIn(1000);
    setTimeout('oldSlide('+lastSlide+');', 1000);
}
function oldSlide(lastSlide) {
    $('#slider_'+lastSlide).fadeOut(1000);
}
setInterval("nextSlide();", 5000);