li.chat a {
display: block;
    padding-top: 21px;
    width: 23px;
    height: 0;
    overflow: hidden;
    background: red;
    text-indent: -9999px;
    background: url(https://ncpa.org/themes/ncpa/images/icon-chat.svg) no-repeat center center;
    background-size: 21px;
}