Wikipedia, the popular online encyclopedia, and many other websites went black on Wednesday as part of a protest against the internet piracy legislation being considered by the US Congress.

Google slapped a virtual black tape across the word 'Google' on its home page, as if it were muffled, although it continued to be available for search.

Wikipedia, the tenth most popular website in the US, shut down most of its English-language services and replaced its familiar white and gray design with a black homepage featuring information about the bills.

The protest is against the Stop Online Piracy Act (Sopa) and the Protect IP Act (Pipa), the legislations that are backed by major American media companies.

'Student warning! Do your homework early. Wikipedia protesting bad law on Wednesday!,' warned Wikipedia founder Jimmy Wales on Twitter, and with that, one of the most heavily visited websites began a 24-hour 'blackout.'

The founders of Google, Twitter, Wikipedia, Yahoo! and other Internet giants said in an open letter last month the legislation would give the US government censorship powers 'similar to those used by China, Malaysia and Iran.'

'We oppose these bills because there are smart, targeted ways to shut down foreign rogue websites without asking American companies to censor the Internet,' a Google spokesman said Tuesday.

Social news site Reddit said it will be blacked out for 12 hours, starting at 8 am ET.

The two bills, supported mainly by the entertainment industry, are aimed at stopping illegal downloading and streaming of movies and TV shows. But many in the tech world — including giants Google and Facebook — say the legislation would let federal authorities shut down portions of the Internet without due process, and fundamentally alter the Internet's ability to provide a platform for free speech.

'This is an extraordinary action for our community to take,' Wikipedia's Wales said earlier in the week about the blackout, adding, '...we simply cannot ignore the fact that Sopa and Pipa endanger free speech both in the United States and abroad, and set a frightening precedent of Internet censorship for the world.'

Tech website Boing Boing also went black, saying in part: 'Boing Boing is offline today, because the US Senate is considering legislation that would certainly kill us forever. The legislation is called the Pritect IP Act (PIPA), and would put us in legal jeopardy if we linked to a site anywhere online that had any links to copyright infringement.'