if (is_win || is_ie)

  {

  document.write('<link rel="StyleSheet" href="/css/pc.css" type="text/css">');

  }

  else if (is_mac)

  {

  document.write('<link rel="StyleSheet" href="/css/mac.css" type="text/css">');

  }

  else

  {

  document.write('<link rel="StyleSheet" href="/css/other.css" type="text/css">');

  }