.callbacks {
    position: relative;
    list-style: none;
    overflow: hidden;
    width: 100%;
    padding: 0;
    margin: 0;
}

.callbacks_nav {
    position: absolute;
    -webkit-tap-highlight-color: rgba(0,0,0,0);
    top: 44%;
    left: 0;
    opacity: 0.3;
    z-index: 3;
    text-indent: -9999px;
    overflow: hidden;
    text-decoration: none;
    height: 12%;
    width: 3%;
    background: transparent url("../images/themes.png") no-repeat left top;
    background-size: 218% 87%;
}

    .callbacks_nav:active {
        opacity: 1.0;
    }

    .callbacks_nav.next {
        left: auto;
        background-position: right top;
        right: 0;
    }