[Rails-docs] Guides not linked from top menu

I've noticed there are some existent guides that are not linked from
the top menu, "Guides index", like:

  http://edgeguides.rubyonrails.org/active_support_core_extensions.html
  http://edgeguides.rubyonrails.org/ajax_on_rails.html
  http://edgeguides.rubyonrails.org/initialization.html

Is that a case of missing links or is there any reason for them not to
be linked?

They are not ready.

Ryan can't complete the initialization guide, AS core extensions is
work in progress, and the one about Ajax needs to be reviewed, but
first updated to Rails 3.

OK.

Some of them have XHTML validation errors but as they are not so
public yet, I think the best option is wait for them to be finished
and fix them later, if needed.