Interesting compilation of extra-biblical texts. The site includes the Dead Sea Scrolls, but that is an exception. Most of the texts are from the various groups falling under the umbrella term "Gnostic," a peculiar quasi-polytheistic and highly mystical variant of Christianity. In addition to documenting ancient Gnosticism, this site also seems to encourage its practice in the modern world. This is one of the oldest such websites, being first set up in 1994.
To the extent that this website articulates its own views I consider it less trustworthy, simply because I haven't gone through and confirmed every statement. But that is just personal scruple.
However religiously bizarre these writings might be, they are certainly of great historical interest. What better source could there be for finding out what the much maligned Mandaeans, Manichaens, Cathars, etc. actually believed than their own sacred texts? And if that isn't satisfactory to you, they have an enormous archive of early writings devoted to attacking gnosticism. Such candid objectivity is hard to find in most religious sites.
There are no viruses or grossly explicit content that I could find, although is some quarters the writings lapse into some odd sex mysticism.