Bucky has posted elsewhere so I know he/she isn't the typical spammer we find in these parts.
The "Emerald Tablets" this web site is implying a relationship to are the supposed teachings of the great Hermes, a man who became canonized as the God Thoth as well as in the form of Hermes & Mercury -- the messenger of the gods.
It's been years since I've dealt with this topic so I really can't shine too focused a light on things, at a cursory glance I'm seeing a New Age variation to classic Hermetic thinking -- an attempt to distance true Hermetics from its Occult standing you might say. Bottom line is, you will learn far more about true Hermetics by starting with the Kybalion ( and )
I can't recall if the actual emerald tablets were found or are simply alluded to in other writings, the lore is that Hermes Trismegistus ( -- one of several names associated with the same character; this is the Greek inference) composed a library of knowledge -- a "bible" of sorts which serves as the foundation of both, physical/carnal science as well as spiritual & mental science a.k.a. Metaphysics. These writings were set onto tablets of emerald and in some forms of the tale there are likewise gold & silver "leaves".
Depending on the lore you listen to, it is believed that the true library is hidden in a room resting between the paws of the Sphinx . . . then again, there secrets of Atlantis, true Astrology and proof that ET & friends populated the earth can likewise be found on this same site . . . if we are to believe the hundreds of theories and psychic impressions that have been taught over the past 200 or so years (mainly). I Nearly Forgot. .
. this same material is where "The Secret" evolved out of.