Wikipedia has shut down its English-language website in protest against anti-piracy legislation currently making its way through US Congress.
More than 7,000 websites, including popular sites Reddit, Mozilla and Twitpic, are due to follow suit, while search engine Google has marked the protest by displaying a black banner on its homepage.
Sites in opposition to the measures will either be "going dark" or post information to educate visitors about bills H.R. 3261, the Stop Online Piracy Act (Sopa), and S. 968, the PROTECT IP Act (PIPA), two pieces of legislation meant to curb copyright infringement.
However many Wikipedia users have been quick to work out ways around the blackout, including using mobile phone sites or pressing the "escape" button while logging onto the site.
While many in the US may support the privacy bill's intentions, opponents and civil libertarians are worried that their passage would give the government powerful censorship tools that could threaten free speech.
When a site "goes dark," or participates in a "blackout," the site will in some way restrict its usual content. For example, the English-language version of Wikipedia, which will be dark from midnight January 18 until midnight January 19, will feature information about SOPA and PIPA and encourage visitors to contact their representatives, in place of its usual encyclopedia entries.
Similarly, visitors to Imagur's photo gallery will find information about the legislation and "a message about how the PIPA/SOPA legislation threatens sites like Imgur" as well as "methods to take action," according to the company's blog.
At a speech in Boston last autumn, Eric Schmidt, Google's former CEO and now executive chairman, called SOPA "draconian," CNN reports. Google announced on Tuesday that it would be posting on its homepage a link to information about the proposed legislation, according to The New York Times.
In November, a bevy of large Internet companies, including Facebook, Google, Zynga, Twitter and LinkedIn, published an open letter in the New York Times that said, in part, the companies were "concerned that these measures pose a serious risk to our industry's continued track record of innovation and job-creation, as well as to our Nation's cybersecurity."
AOL, which owns the Huffington Post, also signed the letter.
There are several ways you can get involved in the SOPA/PIPA protests. SopaStrike.com offers instructions on how to black out your own site. .