var banner = new Array();

banner[0]='https://i.servimg.com/u/f38/17/78/39/82/o_bo10.gif';
banner[1]='https://i.servimg.com/u/f38/17/78/39/82/untitl28.gif';
banner[2]='https://i.servimg.com/u/f38/17/78/39/82/untitl27.gif';

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