if( navigator.userAgent.indexOf('iPhone') > 0 ||
    navigator.userAgent.indexOf('iPod') > 0   ||
  ( navigator.userAgent.indexOf('Android') > 0 && navigator.userAgent.indexOf('Mobile') > 0)){
  document.write('<meta name="viewport" content="width=device-width, initial-scale=1">');

} else{
  document.write('<meta name="viewport" content="width=1024">');

}