var banner = new Array();
banner.push('http://img13.imageshack.us/img13/3544/bannsi.jpg'); 
banner.push('http://img843.imageshack.us/img843/8751/bann3h.jpg');
banner.push('http://img11.imageshack.us/img11/1314/bann5.jpg');
banner.push('http://img163.imageshack.us/img163/3125/bannhdfg.jpg');
banner.push('http://img29.imageshack.us/img29/4830/bann4p.jpg');


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