var banner = new Array();

banner.push('http://i42.servimg.com/u/f42/09/02/13/94/bannia18.jpg');
banner.push('http://i42.servimg.com/u/f42/09/02/13/94/logo_b10.jpg');




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