.bullet_left_event {
    position: absolute;
}
.bullet_left_event div, .bullet_left_event div:hover, .bullet_left_event .av {
    position: absolute;
    /* size of bullet elment */
    width: 19px;
    height: 19px;
    text-align: center;
    line-height: 19px;
    color: white;
    font-size: 12px;
    background: url('/img/slider/b21.png') no-repeat;
    overflow: hidden;
    cursor: pointer;
}
.bullet_left_event div { background-position: -5px -5px; }
.bullet_left_event div:hover, .bullet_left_event .av:hover { background-position: -35px -5px; }
.bullet_left_event .av { background-position: -65px -5px; }
.bullet_left_event .dn, .bullet_left_event .dn:hover { background-position: -95px -5px; }