booksarr=new Array('0471178314','1558608702','0764526413','0735712026','156205810X','0672321513','0910965668','0596004478','1889150290','0471585092','0201353857','0596008031','1575860538','0465051359','0465051367','0672326140','0321344758','0321350316','0125184069','0123706084','0471594032','0131345559','');

if(booksarr.length > 6){
function getRndImg() {
  var rnd = Math.round(Math.random()*(booksarr.length-1));
  return booksarr[rnd]
}
function makeArray() {
  var list = "";
  var arr = new Array();
  cnt = 0;
  while (cnt!=nofRandom) {
    var img = getRndImg();
    if (list.indexOf(img)==-1) {
      arr[cnt++]=img
      list+=img;
    }
  }
  return arr;
}
nofRandom = 6;


arr = makeArray();
for (i=0;i<arr.length;i++)
    {document.write('<iframe src="http://rcm.amazon.com/e/cm?t=masternewmedi&o=1&p=8&l=as1&asins=' + arr[i]+ '&fc1=000000&IS2=1&lt1=_blank&lc1=0000FF&bc1=000000&bg1=FFFFFF&f=ifr" style="width:120px;height:240px;" scrolling="no" marginwidth="0" marginheight="0" frameborder="0"></iframe><br><br>')}

}