document/legacy/2.x/en/css/style.css

/* background behind the logo*/
#header {
    background: black;
    border-color: black;
}

#header-wrapper {
    background: black;
    border-color: black;
}

#chapter p {
    text-align: left;
}

.copy-to-clipboard {
    background-image: none;
    display: none;
}

#body img, #body .video-container {
    margin: auto;
    text-align: left;
    display: inherit;
}