[Zope] - learning by cloning

I´m trying to learn how to work with Zope, by cloning the Zope-homepage, so far I got many hints by viewing the dtml-source. Unfortunately one (at least I) cannot reveal all details. For example, when I didn´t find the source of "sidebar_contents". Also are there more informative debugging-info´s available, than I can look up in the html-source? regards Joachim Schmitz