cleaning up CSS example code

[nevanscott]

I thought it might be nice to standardize a bit on how the CSS coded examples are presented, since there were some inconsistencies before. I made the following changes:

• For multi-line CSS examples, closing brackets are on their own line and not indented, e.g.:

  body {
  color: black;
  }

• Final declarations in a CSS block have a terminating semicolon.
• Properties have a space after the colon.
• I used two spaces for indenting. (It looked like using spaces was the norm, but in some cases it was 3, not 2.)

In one instance (2.1.10), I also cleaned up some of the example HTML in an attempt to improve readability.

If another standard format would be preferable, let me know.

[nevanscott]

Forgot to mention a couple:

I also standardized on lowercase selectors.

And, in 2.1.2, I changed selectors like DIV#col1 to #col1, since an id selector is already unique.