var banner = new Array();

banner[0]='http://img715.imageshack.us/i/newbanner2s.jpg/';
banner[1]='http://img706.imageshack.us/i/newbannerw.jpg/';
banner[2]='http://img149.imageshack.us/i/newbanner3j.jpg/';

document.getElementById('i_logo').src= banner[Math.floor(Math.random()*banner.length)];
setInterval("document.getElementById('i_logo').src= banner[Math.floor(Math.random()*banner.length)];",3000);