.slider_arrow_left, .slider_arrow_right {
    display: block;
    position: absolute;
    /* size of arrow element */
    width: 40px;
    height: 40px;
    cursor: pointer;
    background: url('img/arrows_small.png') no-repeat;
    overflow: hidden;
}
.slider_arrow_left { background-position: 0px 0px; }
.slider_arrow_right { background-position: -40px 0px; }
.slider_arrow_left:hover { background-position: 0px -40px; }
.slider_arrow_right:hover { background-position: -40px -40px; }
.slider_arrow_left.slider_arrow_leftdn { background-position: 0px -80px; }
.slider_arrow_right.slider_arrow_rightdn { background-position: -80px -80px; }