.required-input label {
    position: relative;
}

.required-input label:after {
    content: '*';
    color: rgb(169, 68, 66);
}
.required-input label:hover:after {
    content: 'This field is required!';
    font-weight: normal;
    color: rgb(51, 51, 51);
    position: absolute;
    top: 4px;
    left: 8px;
    min-width: 20ex;
    border: 1px #808080 solid;
    background-color: #ffffcc;
    padding: 4px;
    z-index: 1;
}