var banners = new Array(); 

//banners[0] = '<a href="http://ads.expekt.com/affiliates/redirect.aspx?pid=26099&bid=1545&zid=0"><img src="http://betonline.net.pl/images/expekt720.gif" alt="Expekt" /></a>';
banners[0] = '<a href="http://www.betclic.com/partner.aspx?p=BEE7&z=c3"><img src="http://betonline.net.pl/images/betclic720.gif" alt="Betclick" /></a>';
index = Math.floor(Math.random() * banners.length);
//document.write('<div style="float: left;">' + banners[index] + '</div>');
document.write(banners[index]);