#myBtn {
    display: none;
    width: 40px;
    position: fixed;
    bottom: 20px;
    right: 30px;
    z-index: 999;
    font-size: 40px;
    outline: none;
    color: black;
    text-shadow: 1px 1px 2px rgb(228, 247, 228), 0 0 25px white, 0 0 5px rgb(177, 216, 216);
    cursor: pointer;
    text-align: center;
    line-height: 0;
    opacity: .3;
    animation: fadein 2s;
    -moz-animation: fadein 2s;
    -webkit-animation: fadein 2s;
    -o-animation: fadein 2s;
}

#myBtn:hover {
    color: black;
    opacity: 1;
}

#myBtn span {
    font-size: 14px;
}

@keyframes fadein {
    from {
        opacity: 0;
    }
    to {
        opacity: .3;
    }
}

@-moz-keyframes fadein {
    /* Firefox */
    from {
        opacity: 0;
    }
    to {
        opacity: .3;
    }
}

@-webkit-keyframes fadein {
    /* Safari and Chrome */
    from {
        opacity: 0;
    }
    to {
        opacity: .3;
    }
}

@-o-keyframes fadein {
    /* Opera */
    from {
        opacity: 0;
    }
    to {
        opacity: .3;
    }
}