header {
  background-image: url(/Sistema-en-Mantenimiento.png);
  background-repeat: no-repeat;
  background-size: 100%;
  width: 100%;
  height: 640px;
  #background-position-y: -320px;
}

@media (max-width: 767px){
	header {
  		background-image: url(/Sistema-en-Mantenimiento.png);
 		background-repeat: no-repeat;
  		background-size: 100%;
  		width: 100%;
  		height: 644px;
  		background-position-y: 100px;
	}

}

@media (max-width: 810px){
        header {
                background-image: url(/Sistema-en-Mantenimiento.png);
                background-repeat: no-repeat;
                background-size: 100%;
                width: 100%;
                height: 644px;
                #background-position-y: -50px;
        }

}