body {
  /* Location of the image */
  background-image: url(../img/crinformatica.jpg);
  background-position: center center;
  background-repeat: no-repeat;
  background-attachment: fixed;
  background-size: cover;
  background-color:#ffffff;
}

@media only screen and (max-width: 767px) {
  body {
    background-image: url(../img/crinformatica-m.jpg);
  }
}