when to use what HTML markup documentation/style guide?

Is there some Drupal documentation or a style guide which explains when to use what HTML markup?

For example, when to use <div class="section">, <div class="content">, <p>

• or when to use <h1>, <h2>, <h3>, etc.

• or when to use <div class="description">

I found the Drupal Markup Style Guide, http://groups.drupal.org/node/6355

^ which has some excellent "high level" guide lines - what I can't find is a catalog of Drupal classes and when to use them or what their purpose/meaning/rationale is

Does this exist?