body {
    background-color: white;
    color: #444;
    font-family: sans-serif;
}

h1, h2, h3 {
    color: #069;
}

h3 {
    display: inline-block;
}

a {
    color: darkblue;
}

.element {
    display: block;
}

.element .element, .element .comment, .element .processing-instruction {
    margin-left: 1rem;
}

.valid {
    color: darkgreen;
}

.error, .invalid {
    color: crimson;
}

em {
    font-weight: bold;
}