var alpha = 100;
var cont = 0;
var parado = true;
var t = 50;

function tempo() {
	if (parado) {
		if (t==300) { animar('img2'); }
		if (t==600) { animar('img3'); }
		if (t==900) { animar('img4'); t=0; }
		auto = setTimeout ("tempo();", 10);
		t++;
	}
}

function animar(img) {
    var img1;
    if (img1 == undefined)
        img1 = document.images['img1'];
    if (img1 == undefined)
        return;    
    cont += 5;
	img1.style.filter = 'alpha (opacity=' +alpha+ ', finishopacity=' +alpha+ ', style=1)';
	document.images[img].style.filter = 'alpha (opacity=' +alpha+ ', finishopacity=' +alpha+ ', style=1)';
	if (cont<105) {
		alpha-=5;
		timer = setTimeout ("animar('" +img+ "');", 30);
	} else if (cont>100 && cont<200) {
		some=false;
		alpha+=5;
		timer = setTimeout ("animar('" +img+ "');", 40);
	} else {
		timer = clearTimeout;
		alpha=100;
		cont=0;
		if (!parado) {
			auto = clearTimeout;
			parado = true;
			tempo();
		}
	}
	if (cont == 105) {
		im1 = document.images['img1'].src;
		document.images['img1'].src = document.images[img].src;
		document.images[img].src = im1;
	}
}