I am developing my first Firefox extension, and I decided to use the Help Viewer to display the (minimal) help files I have.
I found that entries in the toc.rdf did not display in the Help Viewer's lefthand panel unless I added an nc:name attribute in each rdf:Description entry (the value being, of course, what text I wanted displayed).
I suggest that the example files here be updated.
There's another problem that I encountered too. My extension provides online dictionary access in Thai, Khmer, Lao and Burmese, so I put all the extension's text strings into an entity file. When I followed the advice at Babelzilla to put the help text into entities as well, I ran into problems.
Eventually I realized that I could not put the help-text strings into a separate file, but had to use the same file already being used for the extension's strings.
I don't know what that restriction comes from, but an awareness of localization issues would seem to be called for in material explaining how one builds help.