#gallery .tile .caption
{
    position: absolute;
    display: block;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    opacity: 0;
    -webkit-transition: opacity .3s;
    -moz-transition: opacity .3s;
    -o-transition: opacity .3s;
    transition: opacity .3s;
    background: rgba(0,0,0,.4);
}
#gallery .tile:hover .caption
{
    opacity: 1;
}
#gallery .tile:hover
{
    cursor: pointer;;
}