CSS, Templates, ...

* A lot of fixes for the CSS.
* Doctype set to html simply.
* Some HTML5 elements mixed into the page.
* Removing H1 from the posts, using article.title instead
* Turn language guessing off for markdown, so we can use the same quotes
for preformatted text everywhere.
* Number of menu items reduced, so it doesn't matter too much for mobile
devices.