var rnd = Math.random() + '.' + (new Date()).getTime(); 

var banner = '<CENTER><A HREF="http://link.bannerlandia.com.ar/r/29675/1?1.3;468;60;' + rnd + '" TARGET="_top"><IMG WIDTH="468" HEIGHT="60" BORDER="0" ALT="Bannerlandia - Haz Click!" SRC="http://banners.bannerlandia.com.ar/s/29675/1?1.3;468;60;' + rnd + '"></A></CENTER>';

document.write(banner);