Some of the documentation pages for Mathematica 10's built-in symbols have an additional "Background & Context" section (just below the Details section) that's reserved for textbook-type information. See for example:
I would like to add this section to some of the symbol pages for my packages. How can I add a new section (that is closed by default) to symbol pages within Wolfram Workbench?
Additional question: will adding this section cause any problems when trying to load these pages from older version of Mathematica like 8 and 9?