Because a lot of those sites on that list don't exist any more and some have 6bone (3ffe::/16) addresses; ipv6.org is pretty much unmaintained unfortunately. At the bottom it states: $Id: v6-www.html,v 1.93 2003/03/21 06:14:16 map Exp $ That is 5 years ago and even 3 years before the 6bone got shut down. If you want to figure it out yourself what happens, try a traceroute6 (Linux/*BSD/etc) or tracert6 or tracert on Windows.