Pics = new Array(2); 
Pics[0]='<a href="http://www.kalod.com"><img src="banner_kalod.jpg" alt="Kalod.com" width="470" height="62" /></a>'; 
Pics[1]='<a href="http://chillijulie.cz"><img src="banner_chilli.jpg" alt="ChilliJulie.cz" width="470" height="62" /></a>'; 
document.write(Pics[Math.floor(Math.random() * Pics.length)]);