Here are the sources of the website of the book
To update index.html one needs to update index.htpl and then type
make index.html.
After updating snippets in folder ../coq/ one needs type make iclean to clean
up index-related files, then make sclean to clean up the snippets/
directory, and then make index.html to generate new index.html. Then one
needs to commit the changes including index.htpl, index.html, and
the snippets/ directory.
To update all parts of the index.html file one needs type
make clean && make all.