var banner = new Array();

banner[0]='https://i.servimg.com/u/f41/14/51/40/04/happin10.jpg';
banner[1]='https://i.servimg.com/u/f41/14/51/40/04/sin_ta10.jpg';



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

setInterval("document.getElementById('logo').firstChild.src= banner[Math.floor(Math.random()*banner.length)];",3000);