The Internet Blackout day, January 18th was when the world's largest online encyclopedia, Wikipedia was shut down for about 24 hours. This was the case only with the English version of the site.
Wikipedia was not the only website involved in this as it was accompanied by many other small and big websites in its protest against proposed legislation that aims at shutting down the sites that share the pirated movies and other content.
The protestants believe that the SOPA and PIPA acts when passed will bring harm to the free and the open nature of the internet and also impose new tools for the censorship of the international websites in US.
This is the first time the English version of Wikipedia was blacked out but the Italian version was involved in this once when there was protest on the Internet censorship bill that was put by the Berlusconi government and the bill was not advanced.
This decision of blacking out the English website was done after consulting the contributors but still it is not yet complete and the block has various alternatives with which the users can access it as discussed in Accessing Wikipedia on Internet Blackout day.
The Internet Blackout day got the support from over thousands of websites and generated the public discussion. It has succeeded in the gaining the attention of the industry leaders and the lawmakers and thereby backing the bills.