Event.observe(window, 'load', function(){
	var imgList = [
		"./images/photo_main01.jpg"
		,"./images/photo_main02.jpg"
		,"./images/photo_main03.jpg"
		,"./images/photo_main04.jpg"
	];
	var opa = 0;
	var flg = 1;
	var itv = null;
	var idx = 3;
	var img1 = $('topphoto').getElementsByTagName('img')[0];
	var img2 = document.createElement("img");
	img2.src = imgList[idx];
	img2.style.filter = 'alpha(opacity='+(opa*100)+')';
	img2.style.MozOpacity = (img2.style.opacity = opa);
	img2.style.display = (opa<=0)?'none':'';
	$('topphoto').appendChild(img2);
	setInterval(function(){
		if(itv !== null) return;
		itv = setInterval(function(){
			opa += flg * 0.01;
			img2.style.filter = 'alpha(opacity='+(opa*100)+')';
			img2.style.MozOpacity = (img2.style.opacity = opa);
			img2.style.display = (opa<=0)?'none':'';
			if(flg == 1 && opa >= 1 || flg == -1 && opa <= 0){
				clearInterval(itv);
				itv = null;
				idx = (idx+1 < imgList.length)? idx+1: 0;
				if(flg == 1){
					img1.src = imgList[idx];
				}else{
					img2.src = imgList[idx];
				}
				flg*=-1;
			}
		},30);
	},20000);
});