.img-div-center{
height: 800px;
  position: relative;
}
.img-centro-vert-hor{
  width: auto;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}
/* For mobile devices */
@media only screen and (max-width: 767px) {
  body {
    /* The file size of this background image is 93% smaller
     * to improve page load speed on mobile internet connections */
    background-image: url(loading.gif);
  }