var banner = new Array();

banner[0]='http://ups.imagup.com/multi/1249457542_banniere3.jpg';
banner[1]='http://ups.imagup.com/04/1249458034_banniere 5.jpg';
banner[2]='http://ups.imagup.com/multi/1249457542_banniere4.jpg';

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