Gatti,
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script src='http://code.jquery.com/jquery-latest.js'></script>
<style type='text/css'>
div{
width: 300px;
height: 100px;
background-color: #FFFF00;
position: fixed;
top: 0;
left: 0;
right: 0;
bottom: 0;
margin: auto;
}
#div2{
background-color: #3399FF;
}
</style>
<script type='text/javascript'>
$(function() {
function b() {
a = a.reverse();
$(a[0]).fadeOut(400).delay(5000).fadeIn(400, b)
}
var a = ["#div1", "#div2"];
b()
});
</script>
</head>
<body>
<div id="div1"></div>
<div id="div2"></div>
</body>
</html>