IPv6 configuration on Mac OS X

How can I enable IPv6 on Mac OS X?

IPv6 enabled but I cannot access IPv6 websites. What is the problem?

On the Mac OS X, the Safari and Internet Explorer browsers always prefer to use IPv4 over IPv6. On Firefox the behaviour is the same, but with Firefox you can change thisby entering the URL "about:config", then changing the value of "network.dns.disableIPv6" to "false".