Apple Safari IPv6 hack (posted 2004-01-28)
IPv6-enabled operating systems such as Windows, Linux and FreeBSD all come with a web browser that also supports IPv6 and prefers IPv6 when both IPv4 is available. Things are slightly different with Safari, Apple's browser application. Initially, Safari only supported literal IPv6 addresses and some corner case DNS names. In the current version, Safari will do IPv6 if no IPv4 address is available, but it won't prefer IPv6 over IPv4 or fall back to IPv6 when IPv4 doesn't work.
However, Nicholas Humfrey has come up with a trick. By enabling Safari's debug mode and switch off one of the two HTTP loaders that are normally used, Safari will prefer IPv6 when it's available. See the Mac OS X hints article that Nick posted for the details.