Bookmarks in non-file buffers?

[Dmitri Minaev]

Is there a way to save the current position (by placing a bookmark or
in any other way) in a buffer that is not associated with a file?
Namely, I'm interested in w3m buffers, pdftotext output and text files
extracted from zip archives in zip-archive mode. Of course, besides
the text position (line number) such bookmarks should contain the
information on how the text was produced.

-- 
With best regards,
Dmitri Minaev

Russian history blog: http://minaev.blogspot.com