tooltip.css

/* https://pixelbar.be/blog/css-profi-tip-tooltip-attributen/ */
.tooltip {
    position: relative;
    text-decoration: none;
}
.tooltip:after {
    content: attr(data-tooltip);
    position: absolute;
    bottom: 100%;
    left: 20%;
    background: #ffcb66;
    padding: 5px 15px;
    color: black;
    -webkit-border-radius: 10px;
    -moz-border-radius : 10px;
    border-radius : 10px;
    white-space: nowrap;
    opacity: 0;
    -webkit-transition: all 0.4s ease;
    -moz-transition : all 0.4s ease;
    transition : all 0.4s ease;
}
.tooltip:before {
    content: "";
    position: absolute;
    width: 0;
    height: 0;
    border-top: 20px solid #ffcb66;
    border-left: 20px solid transparent;
    border-right: 20px solid transparent;
    -webkit-transition: all 0.4s ease;
    -moz-transition : all 0.4s ease;
    transition : all 0.4s ease;
    opacity: 0;
    left: 30%;
    bottom: 90%;
}
.tooltip:hover:after {
    bottom: 100%;
}
.tooltip:hover:before {
    bottom: 70%;
}
.tooltip:hover:after, a:hover:before {
    opacity: 1;
}