var cssnumber = Math.floor(Math.random()*9+1); 
  if (cssnumber == 1)
      display = "http://ooikenji.jp/bgp/bg_position_1.css";
  else if (cssnumber == 2)
      display = "http://ooikenji.jp/bgp/bg_position_2.css";
  else if (cssnumber == 3)
      display = "http://ooikenji.jp/bgp/bg_position_3.css";
  else if (cssnumber == 4)
      display = "http://ooikenji.jp/bgp/bg_position_4.css";
  else if (cssnumber == 5)
      display = "http://ooikenji.jp/bgp/bg_position_5.css";
  else if (cssnumber == 6)
      display = "http://ooikenji.jp/bgp/bg_position_6.css";
  else if (cssnumber == 7)
      display = "http://ooikenji.jp/bgp/bg_position_7.css";
  else if (cssnumber == 8)
      display = "http://ooikenji.jp/bgp/bg_position_8.css";
  else if (cssnumber == 9)
      display = "http://ooikenji.jp/bgp/bg_position_9.css";
  else
      display = "bgp/none.css";
  var css = '<';
  css+='link rel="stylesheet" href=' + display + ' \/';
  css+='>';
document.write(css);