This page is basically an author (James Wood, retired trial lawyer) publicizing his own self-published book Egypt´s Great Pyramid of Knowledge (2007, Author House)
We may sometimes classify misunderstood facts as being mysterious. I think that has been an important factor in the study of ancient Egypt. When skilled Egyptologists and archeologists are confronted with mega monuments that have no historical data to explain their existence they must use their research to come up with answers. They are very good at it but with no actual facts by which to compare results there is no sure way to know what the truth is. This leaves the door ajar for a lot of second-guessing and speculation. It also creates a fertile ground for debate.
As far as I can tell from the rest of this page the author's main purpose is to speculate about the function of the Great Pyramid, but he also appears to consider how the pyramid was built and suggests locations for chambers that were used to store documents.