Fixing #230; add a scrollbar to the PM popup dialog if necessary. This wasn't as easy as I thought. Had to wrap the PM text in a div with its styling (max-height and overflow). If I then resized the dialog, I'd get two scrollbars. So for now, made the dialog non-resizable.

div.potd-details {
    text-align: center;
}
div.potd-details p.caption {
    font-weight: bold;
}
div.potd-details p.details {
    font-style: italic;
    font-size: smaller;
}