/* Element to be underlined */
.jquery-underline-container {
    position: relative;
}

/* <span> to hold the underline */
.jquery-underline {
    position: absolute; 
    display: block;
    top: 0px; 
    left: 0px; 
    width: 100%; 
    height: 100%; 
    border-bottom: 4px solid #898989;
}