.center-video { 
    margin-left: auto;
    margin-right: auto;
    display: block;
    height: auto;
    width: 100%;
    max-width: 500px;
}

.center-block { 
    margin-left: auto;
    margin-right: auto;
    display: block;
    height: auto;
    width: 100%;
    max-width: 500px;
}