Restore accessible `<form>` markup. Only use CSS to alter its visuals.
Make entire "Previous/Next" buttons clickable, not just their text.

Also corrects indentation in the HTML. (But no functional HTML change.)
Use `<span>` rather than a hard break (`<br>`) to create newline effect.
Put main Tumblr content headings on same line when there are multiple.
Remove `<br>`s, use `<span>` as `<div>` is illegal, add day count.