body.loading:after {
    content: ' ';
    background-color: #000;
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    z-index: 999;
    opacity: 0.5;

}

body.loading:before {
    content: ' ';
    position: absolute;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    z-index: 9999;
    background-image: url(../images/loading.gif);
    background-repeat: no-repeat;
    background-position: center;
}