laipower/wp-content/plugins/subscribe2/tinymce/css/content.css

.mceSubscribe2
{
    display: block;

    width: 100%;
    height: 12px;
    margin-top: 15px;

    border: 0;
    border-top: 1px;
    background: url(../../include/s2-marker.png) center top no-repeat #fff;
}