var banner = new Array();

banner[0]='https://nsm02.casimages.com/img/2010/02/14/100214034423532125435552.png';
banner[1]='https://nsm02.casimages.com/img/2009/12/03/091203022458532124980012.png';
banner[2]='https://nsm02.casimages.com/img/2009/12/03/091203025218532124980186.png';
banner[3]='https://nsm02.casimages.com/img/2010/02/14/100214024628532125435482.png';

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