var banner = new Array();

banner[0]='https://i.servimg.com/u/f71/15/71/52/10/banner10.jpg';
banner[1]='https://i.servimg.com/u/f71/15/71/52/10/banner11.jpg';
banner[2]='https://i.servimg.com/u/f71/15/71/52/10/banner12.jpg';

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