var banner = new Array();

banner[0]='http://img683.imageshack.us/img683/5291/bannerinno.jpg';
banner[1]='http://img22.imageshack.us/img22/3308/bannerinno2.jpg';
banner[2]='http://img22.imageshack.us/img22/285/bannerinno3.jpg';

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