var banner = new Array();

banner[0]='http://i54.tinypic.com/fktm5j.png';
banner[1]='http://i56.tinypic.com/9huqed.png';
banner[2]='http://i54.tinypic.com/jg1pxi.png';
banner[3]='http://i53.tinypic.com/icmkd3.png';
banner[4]='http://i52.tinypic.com/2dbs1ex.png';
banner[5]='http://i51.tinypic.com/2jfljdi.png';

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