var banner = new Array();

banner[0]='http://www.freewebs.com/orishas/LogoEdited2010.png';
banner[1]='http://www.freewebs.com/orishas/Logo-New2010-FIXED.png';
banner[2]='http://www.freewebs.com/orishas/LOGOBLACK.JPG';
banner[3]='http://www.freewebs.com/orishas/Logo-Gamboa%20y%20Lopez.PNG';

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