[...] lots of beginning HTML dreck, doctype, Javascript

      banner ad rotation stuff, etc.

<!-- END MAIN HEADER CODE -->

I'd like to throw everything above the comment tag above, away, 
keeping everything below this point, up to the end of the bottom 
navigation elements. 

<!-- TOP CHAPTER/SECTION NAV CODE -->
HTML for content-specific navigation in the body of the page. 
I want to keep this
<!-- END TOP CHAPTER/SECTION NAV CODE -->

<!-- BEGIN CHAPTERTITLE -->
Title of the body of content I want to keep is here
<!-- END CHAPTERTITLE -->

Some other related HTML goes here, I need to keep this

<!-- BEGIN CHAPTER -->  
The actual content itself is here, I need to keep this also

<!-- END CHAPTER -->

<!-- BOTTOM CHAPTER/SECTION NAV CODE -->
Duplicated elements of content navigation here, 
same as on the top of the content itself. I'd like to keep this too. 

<!-- END BOTTOM CHAPTER/SECTION NAV CODE -->

Everything after this last comment tag, I need to throw away.