@media (max-width: 640px) {

 /* Un message personnalisé */
 body:before {
   content: "Version mobile du site";
   display: block;
   color: #777;
   font-style: italic;
 }
}
@media (max-device-width:768px) and (orientation: landscape) {
  html {
   -webkit-text-size-adjust: 75%;
   -ms-text-size-adjust: 75%;
  }
}