paper block for little snippets for webpublishing

[Music Teacher]

Hello dear helpers and experts,

I did found in the doc or in snippets how to make snippets (png or
gif) for webpublishing, like in the manual.
I mean, something like:

music-to-top-edge = 3 \mm
music-to-left-edge = 4 \mm

etc
or something like that. And I dont understand in a snippet like the
first one in:
http://lilypond.org/doc/v2.12/Documentation/user/lilypond-big-page#Changing-multiple-pitches
gives this pict.

It would to put in wikipedia articles.

Thanks in advance

Francois