css solution to hide div after x amount of seconds

Answer 1

Closest you can come with css only is this..it might be improved further but this as it's..

http://jsfiddle.net/techsin/7g7ofazj/

.red {
    background-color: red; width: 100px; height: 100px;
    -webkit-animation: ani 1s forwards;
}

@-webkit-keyframes ani {
    89%  {opacity:1;height: 100px;}
    90%  {opacity:0; height: 0;}
    100%  {opacity:0; height: 0;}
}

And if you wanted to do with javascript/jquery..

you would do this..

var ele = $(".hide_after_90_seconds");
setTimeout(function() { ele.hide(); }, 9000);