/* Image with 'data' attribute is hidden */
img[data-lazy-src] {
/* we set the opacity to 0 */
   opacity: 0;
}
/* Image without 'data' attribute is (or becomes) visible */
img.lazyloaded {
/* prepare the future animation */
   -webkit-transition: opacity .5s linear 0.2s;
       -moz-transition: opacity .5s linear 0.2s;
                 transition: opacity .5s linear 0.2s;
/* we set the opacity to 1 to do the magic */
   opacity: 1;
}