var banner = new Array();

banner[0]='http://img854.imageshack.us/img854/8181/montaje222.png';
banner[1]='http://img268.imageshack.us/img268/7046/montaje4.png';
banner[2]='http://img847.imageshack.us/img847/1514/montaje32.png';


document.getElementById('logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];

setInterval("document.getElementById('logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];",5000);