The workshop homework for the January meeting is to consider and answer this question on usage. I will give my version of the answer (not necessarily an authoritative answer) as extra credit at the January meeting at 8:45. If you do not make it to the meeting in time, I will post my answer here on the site after the meeting.
As an incentive to have you ponder this metaphysical query, I have the following proposition: Anyone who e-mails me a reasonable effort at an answer will be entered in a raffle for a used-but-in-good-shape copy of the first edition of O'Reilly's CSS Pocket Reference. The second edition is now out, but the first is fine as a quick check of basic CSS.
Answers don't have to be right, just a good try. Entries must be received by me by the time I turn off my computer Friday night, January 14. So assume 9:00 to be safe.
I will pick a name Saturday out of all the entries. If you are not present, I will hold the book until February. If you are not present for that meeting, I will raffle it off to all who are in attendance at that time. Seems a fair way to do it.
Give it a try and let me see what you think.