var banners = new Array(); 
banners[0] = '<iframe src="http://pub.betclick.com/pub.aspx?p=BEE7&z=c17 " height="250" width="300" frameborder="0" scrolling="NO"></iframe>';

index = Math.floor(Math.random() * banners.length);
if (typeof banners[index] == 'object') document.write(banners[index][0] + '<span class="text">' + banners[index][1] + '</span>');
else document.write(banners[index]);