#leftsss {
    animation: left 5s forwards;
}
#rightss {
    animation: right 5s forwards;
}

@keyframes left {
    from {
        transform: translateX(-1000px); /* Capital 'X' is required */
    }
    to {
        transform: translateX(0px);
    }
}

@keyframes right {
    from {
        transform: translateX(1000px); /* Capital 'X' is required */
    }
    to {
        transform: translateX(0px);
    }
}