var how_many_ads = 1;
var now = new Date()
var sec = now.getSeconds()
var ad = sec % how_many_ads ;
ad +=1;





if (ad==1)
document.writeln('<iframe src=http://www.parquestematicos.org/Arriba-Megabanner.asp width=728 height=90 frameborder=0 marginheight=0 marginwidth=0 scrolling=no></iframe>');
if (ad==2)
document.writeln('<iframe src=http://www.parquestematicos.org/Arriba-Megabanner2.asp width=728 height=90 frameborder=0 marginheight=0 marginwidth=0 scrolling=no></iframe>');

if (ad==3)
document.writeln('<iframe src=http://www.parquestematicos.org/AdSense-728x90.asp width=728 height=90 scrolling=no frameborder=0 border=0></iframe>');

if (ad==4)
document.writeln('<iframe src=http://www.codigobarras.com/share-ht/jedis/ad_tpl.php?ic=1957&amp;r=4699 width=728 height=100 frameborder=0 marginwidth=0 marginheight=0 scrolling=no ></iframe>');