Update CSS files.

* trim trailing spaces
* be explicit with the `background-color` property
* use the shortened hex for white and black colors
* remove units from zero
Add missing quotes in font names.
Be more consistent with the border property.
printable.css: Fix `border` shorthand.

The properties need to be in order: width style color.
Fix comma being used instead of semicolon.
yslow.css: move vendor prefixed property before the unprefixed one.
Use the shorthand for list-style.