findRightAndInsertAd();

function getSquareAd(){
  var random=Math.random();
  var squareAd = document.createElement("div");
  squareAd.id = 'squareAd';
  squareAd.innerHTML = '<IFRAME WIDTH="200" HEIGHT="200" MARGINWIDTH="0" MARGINHEIGHT="0" HSPACE="0" VSPACE="0" FRAMEBORDER="0" SCROLLING="NO" BORDERCOLOR="#000000" SRC="http://ad.nttnavi.co.jp/html.ng/site=Nifty&spacedesc=nfishing-rect&tocode=SJIS&transactionID='+random+'?"></IFRAME>';
  return squareAd;
}

function findRightAndInsertAd(){
  var right = document.getElementById('right');
  if(right){
    right.insertBefore(getSquareAd(), findSidebarTop(right))
  }else{     setTimeout("findRightAndInsertAd()", 10); 
  }
}

function findSidebarTop(element){
  var divs = element.getElementsByTagName('div');
  var sidebarTop;
  for(var i=0; i<divs.length; i++){
    if(divs[i].className == 'sidebar-top'){
      return divs[i];
    }
  }
}