if (navigator.userAgent.indexOf('Android') != -1){
    document.write('<link rel="stylesheet" type="text/css" href="css/smartphone.css">');
  }else if(navigator.userAgent.indexOf('iPhone') != -1){
    document.write('<link rel="stylesheet" type="text/css" href="css/smartphone.css">');
  }else{
    document.write('<link rel="stylesheet" type="text/css" href="css/pc.css">');
  }