Fig 1. A slab of marble, embossed into the wall of a temple.
The above carving was identified as being not merely a tutorial, but also to conceal a secret number. Sacred geometrical principles have been used, and the appropriate region is highlighted.
Those strong of heart may replace "index.html" with "whatever_you_think_the_answer_is.html"
Those who fear 404 pages, may try "clue1.html" to "clue3.html"