var now = new Date();

   var sec = now.getSeconds();

   var ses = 12;     

   rnd_number = Math.floor(sec/ses);

if (rnd_number == 0)
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if (rnd_number == 1)
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if (rnd_number == 2)
   document.write('<a href="http://www.accademiageograficamondiale.com" target="_blank"><img border="0" src="agm.gif"></a>');
if (rnd_number == 3)
   document.write('<a href="http://freeweb.supereva.com/palermo.freeweb/altro/kritik.htm" target="_blank"><img border="0" src="pubbli/kritik.gif" alt="Newsletter di arte, cultura e spettacolo. Per riceverla clicca qui"></a>');
if (rnd_number == 4)
   document.write('<a href="http://www.islepark.it" target="_blank"><img border="0" src="logoparco-small.gif"></a>');