var num, numx10, rndnum, roundnum;
  rndnum=Math.random();
  numx10=rndnum*10;
  roundnum=Math.round(numx10);
  if((roundnum > 0) && (roundnum <= 3))  {
    document.write('<a href="https://uskkastore.uskka.com/catalog/index.php"><img src="images/uskkassbookad.jpg" border="0" height="334" width="200"></a>');
  }
  if((roundnum > 3) && (roundnum <= 7))  {
    document.write('<a href="https://uskkastore.uskka.com/catalog/index.php"><img src="images/uskka90dayad.jpg" border="0" height="382" width="200"></a>');
  }
  if((roundnum > 7) && (roundnum <= 10))  {
    document.write('<a href="https://uskkastore.uskka.com/catalog/index.php"><img src="images/uskkanutritionbookad.jpg" border="0" height="275" width="200"></a>');
  }