The technology community and U.S. lawmakers have reacted strongly to online anti-piracy legislation under consideration.
The legislation is known as the Stop Online Piracy Act (SOPA) in the House of Representatives and Preventing Real Online Threats to Economic Creativity and Theft of Intellectual Property Act (PIPA) in the Senate
Sponsors of the bills in the entertainment, publishing and pharmaceutical industries say they are critical to curbing online piracy which costs them billions of dollars a year.
However technology companies including Google, Facebook, Yahoo, Twitter, eBay and AOL say the bills undermine innovation and free speech, and could compromise internet function.
Protests have swept the web, with online encyclopaedia Wikipedia shutting its English-language content for 24 hours in a "blackout" protest, while other websites used black censorship bars to raise the profile of their protest.
Craigslist, the free internet classifieds site, also went black in protest, while Google's home search page included a black bar slapped over its logo and asked readers: "Tell Congress: Please don't censor the web!"
"We can't let poorly thought out laws get in the way of the Internet's development," Facebook chief executive Mark Zuckerberg said in a statement.
Many websites participating in the blackout urged users to contact legislators, resulting in several sponsors in the Senate announcing their withdrawal of support for the bill.
However the entertainment industry has fought back, with studio- and union-supported group Creative America launching television and digital campaigns to gather support from votes.
Former Senator Chris Dodd, who now chairs the Motion Picture Association of America, labeled the blackout a "gimmick" and called for its supporters to "stop the hyperbole and PR stunts and engage in meaningful efforts to combat piracy."
The SOPA and PIPA legislation would use court orders to curb access to foreign websites "dedicated to theft" through techniques such as disabling links to those sites.
They also cut off U.S.-based payments processing for those overseas websites that traffic in stolen content or counterfeit goods.
Copyright holders and entertainment companies say the law is needed to curb online piracy and save billions of dollars as many legal copyright remedies aren't effective against big foreign sites such as PirateBay.
Technology companies say they too oppose such piracy but argue that the proposed laws go too far.
They say it would undermine an existing law called the Digital Millennium Copyright Act and its "safe harbour" provisions for websites and others that act in good faith in their handling of third-party content on their sites.
However their opponents argue that the bills simply fill gaps in the DMCA and wouldn't affect the safe harbour provisions.
Other criticisms of the bills are that it could encourage frivolous litigation, require extra policing of services for links to overseas pirated content, and that users could still circumvent the new restrictions allowing piracy to still occur.
Bill supporters however say that the difficulty of squeezing large payments out of illegal overseas sites would discourage frivolous litigation, that technology companies would only have to act on overseas pirated content if notified, and that the law would create important tools for fighting online piracy.
The latest developments on the bills includes the decision of U.S. Senate Democratic leader Harry Reid to postpone the Senate vote on the PIPA bill, while the SOPA bill is still before the House Judiciary Committee.
The White House has also expressed objections to the legislation, particularly a provision that would have required internet service providers to cut off access to infringing sites through a technology known as DNS blocking.