This document has TWO parts which is separately edited:
Here the default marker, #-##TYPO3_STATICFILE_EDIT###, is used to identify the content section:

Content with the regular marker in it.

Linking back from here...

Here a custom marker, B-UTTERFLY, used: This marker is a pretty stupid choice because the very word may be used somewhere else in the HTML-file and it should not!

This is the butterfly part:

Link back to the main page.