Tweak old styles to fix the ugliness on mixed-mode pages

I tracked down and fixed the thing which was causing whitespace at the top of many old-theme pages, and made it so the autohide of the topbar (now that it's not `display: fixed`) does nothing.

It's hacky &mdash; there's hardcoded values, there's unused classes, but who gives a fuck, it'll work until the old stuff is phased out