.block_slider {
    float: left !important;
    height: 500px !important;
}

.block_slider:before {
    display: block !important;
}

.block_slider:after {
    display: block;
    position: absolute;
    top: 0;
    right: 0;
    left: 0;
    bottom: 0;
    content: '';
    background: rgba(0,0,0,.3);
}