[whatwg] Clarify how to indicate document hierarchy

[Benjamin Hawkes-Lewis]

Spartanicus wrote:

> I see no guidance of the type you requested in the HTML4 spec.

Example 1:

> Since users often consult documents out of context, authors should
> provide context-rich titles. Thus, instead of a title such as
> "Introduction", which doesn't provide much contextual background,
> authors should supply a title such as "Introduction to Medieval
> Bee-Keeping" instead.

http://www.w3.org/TR/html401/struct/global.html#h-7.4.2

Example 2 (the spec with Multiple Personality Disorder):

> Some people consider skipping heading levels to be bad practice. They
> accept H1 H2 H1 while they do not accept H1 H3 H1 since the heading
> level H2 is skipped.

http://www.w3.org/TR/html401/struct/global.html#h-7.5.5

Example 3:

> Authors should provide a summary of a table's content and structure so
> that people using non-visual user agents may better understand it.
>