var banner = new Array();

banner[0]='http://i17.servimg.com/u/f17/12/67/92/63/d2u2ze12.jpg';
banner[1]='http://i17.servimg.com/u/f17/12/67/92/63/b10.jpg';
banner[2]='http://i17.servimg.com/u/f17/12/67/92/63/banner10.jpg';
banner[3]='http://i17.servimg.com/u/f17/12/67/92/63/mibann10.jpg';

document.getElementById('pun-logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];