var banner = new Array();

banner[0]='http://img148.imageshack.us/img148/8059/hjkhjkhjktyui.png';
banner[1]='http://img88.imageshack.us/img88/6908/gfjhkghkfgkfgkfhlf.png';


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