CSS Cleanup

[oculus42]

Very minor updates:

• Remove useless units on zero values.
• Remove duplicate values.
• Remove invalid Mozilla internal properties.
• Use shorthand on margin and padding in some places.
• Add a few default font families - more needed here.

[palmertab]

Doing some of this stuff has been on my vague todo list now for months now, and then you went and did it, so that's awesome and appreciated!