function adArray() {
 for (i=0; i*2<adArray.arguments.length; i++) {
  this[i] = new Object();
  this[i].src = adArray.arguments[i*2];
  this[i].href = adArray.arguments[i*2+1];
 }
 this.length = i;
}
function getAdNum() {
 dat = new Date();
 dat = (dat.getTime()+"").charAt(8);
 if (dat.length == 1)
  ad_num = dat%ads.length;
 else
  ad_num = 0;
 return ad_num;
}
 
var ads = new adArray(
"http://booksfactory.com/images/dropbox.gif","http://db.tt/3SCtunC",
"http://ecx.images-amazon.com/images/G/01/img10/associates/leaderboard/best-of-2009_468x60.gif","http://www.amazon.com/b?node=2233760011&tag=booksoftheworld&camp=15329&creative=394445&linkCode=ur1&adid=1NHC3WJF5Z26X3GTDCE5&"
);

var ad_num = getAdNum(); 

document.write('<CENTER><TABLE CELLPADDING=0 CELLSPACING=1 BORDER=0><TR><TD>'
+'<A HREF="'+ads[ad_num].href+'" target="_blank"><IMG SRC="'+ads[ad_num].src+'" '
+'HEIGHT=60 WIDTH=468 BORDER=0 name=js_ad></A></TD></TR></TABLE></CENTER>');


link_num = document.links.length-1;

function rotateSponsor() {
 if (document.images) {
  ad_num = (ad_num+1)%ads.length;
  document.js_ad.src = ads[ad_num].src;
  document.links[link_num].href = ads[ad_num].href;
  setTimeout("rotateSponsor()",45000);
 }
}
setTimeout("rotateSponsor()",45000);