body {
    -webkit-animation: fadein .4s;
    -moz-animation: fadein .4s;
    -ms-animation: fadein .4s;
    -o-animation: fadein .4s;
    animation: fadein .4s;
}
 
/* --- ANIMATION ---- */
@keyframes fadein {
    from { opacity: 0; }
    to   { opacity: 1; }
}
@-moz-keyframes fadein {
    from { opacity: 0; }
    to   { opacity: 1; }
}
@-webkit-keyframes fadein {
    from { opacity: 0; }
    to   { opacity: 1; }
}
@-ms-keyframes fadein {
    from { opacity: 0; }
    to   { opacity: 1; }
}​
@-o-keyframes fadein {
    from { opacity: 0; }
    to   { opacity: 1; }
}​