.fondo1{
  background:#464646 url('../img/fondos/1.jpg') no-repeat fixed center; /* Image is centered vertically and horizontally at all times */
  background-size: cover
}

.fondo2{
  background:#464646 url('../img/fondos/2.jpg') no-repeat fixed center; /* Image is centered vertically and horizontally at all times */
  background-size: cover
}