height: min(100%, 600px);

    display: flex;
    flex-direction: column;
}
body {
    flex-grow: 1;
    display: flex;
    flex-direction: column;

}
#content {
    flex-grow: 1;
}
/* Fixes <hr> collapsing to width 0 inside of a flex container */
hr {
    margin-left: 0;
    margin-right: 0;
    align-self: stretch;

<div id="content">

</div>