CSS Tooltip

index.html

<button class="tooltip" tooltip-title="Save">Hover over me</button>

style.css

body{
    padding: 50px;
}
.tooltip {
    position: relative;
}

.tooltip:before {
    content: attr(tooltip-title);
    min-width: 54px;
    background-color: #999999;
    color: #fff;
    font-size: 12px;
    border-radius: 4px;
    padding: 9px 0;
    position: absolute;
    top: -42px;
    left: 50%;
    margin-left: -27px;
    visibility: hidden;
    opacity: 0;
    transition: opacity 0.3s;
}

.tooltip:after {
    content: "";
    position: absolute;
    top: -9px;
    left: 50%;
    margin-left: -5px;
    border-width: 5px;
    border-style: solid;
    border-color: #999999 transparent transparent;
    visibility: hidden;
    opacity: 0;
    transition: opacity 0.3s;
}

.tooltip:hover:before,
.tooltip:hover:after{
    visibility: visible;
    opacity: 1;
}