body.loading .waitingModal {
    display: block;
}

.waitingModal {
    display: none;
    position: fixed;
    z-index: 1000;
    top: 0;
    left: 0;
    height: 100%;
    width: 100%;
    background: rgba( 255, 255, 255, .8 ) url(../Assets/img/Spinner.gif) 50% 50% no-repeat;
}