var banner = new Array();

banner.push('http://img52.imageshack.us/img52/9718/naruto15.jpg');
banner.push('http://img696.imageshack.us/img696/5397/banniren2.png');
banner.push('http://img705.imageshack.us/img705/1605/banniren1.png');

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