Why CSS3 Basic Box Model is "Dangerously outdated"?

Question

These days I'm learning CSS by reading specifications, but I noticed W3C marked CSS Basic Box Model Level 3 as "Dangerously outdated" without any further explanation.

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So my question:

1. What's the reason for considering that specification outdated?
2. Why CSS3 Box Model is Outdated but CSS2.1 box model is not outdated(because they said "see CSS 2.1")?

"Dangerously outdated" is displayed here.

• Matthew: Are you sure it doesn't mean the documentation is dangerously outdated?
• Robert Harvey: I don't see "dangerously outdated" anywhere on the page you linked.
• Sayalic: @RobertHarvey Sorry for confusing description. You can check my EDIT for finding that "Dangerously outdated" comment.
• Robert Harvey: I read that as "They haven't worked on it in a long time, and some browsers probably do things differently." Also note that CSS 2.1 is being edited "in-place." It's not outdated because it is largely complete and in common use.

Answer 1

1. If you see the history of revisions for the working draft you will see the last modification was at 2007年08月09日. In the complete list of CSS drafts you will se the "Basic Box model" draft is the most outdated document, the last in the list after "CSS Multi-column Layout Module" (2011).

2. The CSS 2.1 Box model is almost complete and mature. The majority of modern browsers are fully compliant with CSS 2.1. The current draft needs clarification, proper references to CSS 2.1 adopted/original specifications. In the introduction of the current draft we can read:

   Note: The model in this specification differs from the model described in the CSS level 2 specification [CSS21], because (1) it is generalized to apply also to vertical text and (2) it adds properties to control the marquee effect, (speed, direction, etc.)

• Mason Wheeler: So what's dangerous about it?