a.button-facebook {
    border-color: #3b5998;
    background: #627aac;
    color: #444;
    opacity: 0.6;
    transition: opacity .5s ease-in-out;
    -moz-transition: opacity .5s ease-in-out;
    -webkit-transition: opacity .5s ease-in-out;
}

a.button-facebook:hover {
    background: #3b5998;
    color: #FFF;
    opacity: 1.0;
    transition: opacity .55s ease-in-out;
    -moz-transition: opacity .2s ease-in-out;
    -webkit-transition: opacity .2s ease-in-out;
}