.b-lazy {
  -webkit-transition: opacity 500ms ease-in-out;
     -moz-transition: opacity 500ms ease-in-out;
       -o-transition: opacity 500ms ease-in-out;
          transition: opacity 500ms ease-in-out;
             opacity: 0;
}
.b-lazy.b-loaded {
             opacity: 1;
}