var a=100
var b=0
var c=3
function ff(){
var j
a--
b++
document.getElementById("aa"+c).style.filter="alpha(opacity="+a+")"
document.getElementById("aa"+c).style.opacity=a/100;
if(c==1){j=3}else{j=c-1}
document.getElementById("aa"+j).style.filter="alpha(opacity="+b+")"
document.getElementById("aa"+j).style.opacity=b/100
if(a<0){a=100;b=0;c=j}else{setTimeout("ff()",1)}
}
setInterval("ff()",3000)