var banner = new Array();

banner[0]='http://img189.imageshack.us/img189/904/aqac.png';
banner[1]='http://img641.imageshack.us/img641/7459/qswds.png';
banner[2]='https://i751.photobucket.com/albums/xx155/tahorisan/bannernew2.jpg?t=1292667345';
banner[3]='https://i751.photobucket.com/albums/xx155/tahorisan/bannernew.jpg?t=1292667349';

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