.tooltipimg {
    position: relative;
    display: inline-block;
    border-bottom: 1px dotted black;
}

.tooltipimg .tooltiptext {
    visibility: hidden;
    width: 460px;
    background-color: black;
    color: #fff;
    text-align: center;
    border-radius: 6px;
    padding: 5px 0;
    position: absolute;
    z-index: 1;
    bottom: 100%;
    left: 50%;
    margin-left: -60px;
    /* Fade in tooltip - takes 1 second to go from 0% to 100% opac: */
    opacity: 0;
    transition: opacity 1s;
}

.tooltipimg:hover .tooltiptext {
    visibility: visible;
    opacity: 1;
}