* Remove background color from <screen> elements. It makes them stand
out too much. Some pages have many <screen> elements, listing shell
commands and their output. Having a dark background seems a bit too
distracting.
* Keep the background color for <programlisting> elements, but make it
a bit lighter and add a thin border that is slightly darker than the
highlighting background.
* Change the width of <example>, <note>, <warning> and other block
elements to use a percentage of the page width instead of a
hardcoded pixel-based length.
* Add Wikipedia-inspired coloured backgrounds and thin borders around
<example>, <note>, <warning> and tip elements.
Reviewed by: blackend, gavin, rene
No objections: freebsd-doc
8256de476c