var banner = new Array();

banner.push('http://prem1.hiboox.com/images/0711/91d6c51af79fa662f5dd56eca83e19e1.png');
banner.push('http://prem1.hiboox.com/images/0711/f9c69699d717076fdd72fbb9d5387a89.png');
banner.push('http://prem1.hiboox.com/images/0711/4b8fc22cffcb65df84b6aad989b10a89.png');
banner.push('http://prem1.hiboox.com/images/0711/ebf2bdc998b5a13310260a2373689d1f.png');
banner.push('http://prem1.hiboox.com/images/0711/aa63db056e83fb036e548790a725f22f.png');

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