I noticed that in the original documentation content ( ​http://zoo-project.org/docs ) some part are displayed with red borders, as for instance here: ​http://zoo-project.org/docs/services/zcfg-reference.html#main-metadata-information .

I noticed that the issue occurs in both html and pdf files produced.

I think that using the following:

.. code-block:: none

rather than:

.. code-block:: guess

which is currently used should solve the issue.