#myLink {
    opacity: 0;
}

#myLink:hover {
    opacity: 1;
    -webkit-transition: all 0.2s ease-in-out;
    -moz-transition: all 0.2s ease-in-out;
    -o-transition: all 0.2s ease-in-out;
    transition: all 0.2s ease-in-out;
}

这里有一个jsFiddle来演示：Fiddle