@viewport {
  width: device-width ;
  zoom: 1.0 ;
}
@-ms-viewport {
  width: device-width ;
}
@media screen and (max-width:320px) {
  /* CSS for screens that are 320 pixels or less will be put in this section */
}
@media screen and (min-width:320px) and (max-width:640px) {
  /* for screens that are at least 320 pixels wide but less than or equal to 640 pixels wide */
}
/* code that is here, until the first @media block, will apply to any screen size */
#somethingorother {
  width: 800px ;
}

@media screen and (max-width: 320px) {
  /* comes into effect for screens less than or equal to 320 pixels */
  #somethingorother {
    width: 120px ;
  }
}
@media screen and (min-width: 321px) and (max-width: 480px) {
  /* comes into effect for screens between 321 and 480 pixels (inclusive) */
  #somethingorother {
    width: 320px ;
  }
}
@media screen and (min-width: 481px) {
  /* comes into effect for screens larger than or equal to 481 pixels */
  #somethingorother {
    width: 480px ;
  }
}
@media screen and (orientation:portrait) {
  /* ... */
}
@media screen and (orientation: landscape) {
  /* ... */
} 
@media only screen and (max-width: 480px) {
  /* ... */
} 
@media not (max-width: 639px) {
/* CSS rules for any device that is wider than 639 pixels */
}