The bills, the Stop Online Piracy Act (SOPA) and the Protect Intellectual Property Act (PIPA), were meant to crack down on the online theft of intellectual property. But Internet-related companies argued the bills would also lead to online censorship.
Senate and House leaders announced Friday they were postponing votes on the legislation, until those concerns could be addressed.
The English language version of Wikipedia was replaced with a message that explains the reason for the blackout. They claim 162 million people saw their message, shut down Congress' switch boards and melted their servers.
Reddit.com shut down its social news service for 12 hours. Other sites made their views clear without cutting off surfers.
Google blacked out the logo on its home page, directing surfers to a page where they could add their names to a petition against the bills.
The one-day outage was timed to coincide with key House and Senate committee hearings as they prepare to send the bills to the full floor for debate.
Amid the high-tech campaign against the bills, several lawmakers came out in opposition. At least four Senate Republicans who had previously cosponsored the Senate bill - Orrin Hatch of Utah, Roy Blunt of Missouri, John Boozman of Arkansas and Charles Grassley of Iowa - issued statements Wednesday saying they were withdrawing their support. Democratic Sen. Ben Cardin of Maryland last week said that, after listening to constituent concerns, he could not vote for the Senate bill as it is currently written.
The Associated Press contributed to this report.