(CNN) -- Wikipedia was back Thursday, a day after shutting down the website to protest anti-piracy bills now in Congress.
On the website early Thursday morning was the cryptic message: "Thank you for protecting Wikipedia. We're not done yet."
Clicking on that message takes a Wikipedia viewer to a thank you letter and instructions on how to continue fighting against anti-piracy bills that critics say could amount to censorship.
"Your voice was loud and strong," the message said. "Millions of people have spoken in defense of a free and open Internet."
Wikipedia was among several websites to shut down Wednesday in protest of the bills.
Instead of the usual encyclopedia articles, visitors to Wikipedia's English-language site were greeted by a message about the decision to black out its Web page for an entire day.
However, users were able to access Wikipedia on some smartphones.
The site and several others went dark at midnight Tuesday; others followed suit later in the day.
The protest is in response to the Stop Online Piracy Act bill, a piece of proposed legislation that is working its way through the Congress. A Senate committee approved a similar bill in May called the Protect IP Act, which is now pending before the full Senate.
The controversy over SOPA and PIPA has turned into an all-out war between Hollywood and Silicon Valley. Media companies have united in favor of the bills, while tech's power players are throwing their might into opposing them.
"Both SOPA and PIPA are threats not just to the U.S. economy, and not just to all the jobs that this tech sector creates, but if they had existed, Steve Huffman and I could have never founded Reddit," said Alexis Ohanian, who co-founded the site. Millions visit Reddit to submit interesting links from websites, discuss them and vote on them, he said, calling it "sort of a democratic front page of the web." Reddit also went dark Wednesday morning and was back Thursday.
One member of Congress, Rep. Darrell Issa, R-California, who opposes the bills, said the unprecedented blackouts had "turned the tide against a backroom lobbying effort by interests that aren't used to being told no."
Issa is pushing for consideration of his own plan, the OPEN act, addressing the matter.
CNN's Ed Payne, Julianne Pepitone, John D. Sutter, Ted Barrett and Deirdre Walsh contributed to this report.