The world’s first IPv6 (new version of the Internet Protocol) test will be conducted on June 8, 2011. On that day, major websites and web services such as Google, Yahoo, and Facebook will enable IPv6 for 24 hours on their main websites.
According to Google, the test will affect less than 0.5% of the internet users. In addition, even if IPv6 will be enabled for 24 hours, the old IPv4 will continue to be available.
For your information, “Google has been supporting IPv6 since early 2008, when they first began offering search over IPv6. Since then they’ve brought IPv6 support to YouTube and have been helping ISPs to enable Google over IPv6 by default for their users”. [via]