.preloader {
   position: fixed; /* changed from absolute */
   top: 0;
   left: 0;
   width: 100%;
   height: 100%;
   z-index: 9999;
   background-image: url('loading.gif');
   background-repeat: no-repeat; 
   background-color: #fff;
   background-position: center;
   background-size: 125px 125px;
}