Content-wise,
home.x3dna.org is a
duplicate of
x3dna.org, so both are the homepage of the 3DNA suite of programs, including DSSR and SNAP.
I registered the x3dna.org domain name and has hosted it on a popular shared web hosting service. Later on, I noticed that the 3DNA website is not acceptable from China, presumably due to the politically sensitive contents of other websites. To cater for the increasingly large number of 3DNA users from China, I created the home.x3dna.org sub-domain which is hosted at Columbia University. As a side note, the 3DNA Forum (
forum.x3dna.org) is similarly hosted at Columbia, so it is generally accessible.