var banner = new Array();

banner[0]='http://www.lesitedalex.com/images/XD/images_forum/actuel/banniere01.jpg';
banner[1]='http://www.lesitedalex.com/images/XD/images_forum/actuel/banniere01.jpg';
document.getElementById('i_logo').src= banner[Math.floor(Math.random()*banner.length)];