var banner = new Array();

banner[0]='https://i.servimg.com/u/f86/11/36/70/22/bann_311.jpg';
banner[1]='https://i.servimg.com/u/f86/11/36/70/22/bann_311.jpg';
banner[2]='https://i.servimg.com/u/f86/11/36/70/22/bann_311.jpg';

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