Yahoo has been accused of censorship on its popular photo website Flickr, in a row that has highlighted the issue of copyright in the online age.
Earlier this month photographer Rebekka Gudleifsdóttir discovered that seven of her pictures were reportedly being sold by a UK-based online gallery.
She raised the issue on Flickr but a photo and comments were deleted.
Yahoo, which had no involvement in the row over the sale of the photos, has now apologised for its "mistake".
According to Ms Gudleifsdóttir, online gallery Only Dreemin sold 60 prints of seven of her photos, for more than £2,500, without her consent.
No-one from gallery Online Dreemin was available for comment.
Ms Gudleifsdóttir owns the copyright to all of her photos on Flickr and the website clearly states that people cannot use them without permission.
The gallery withdrew the photos for sale but refused to compensate her, she said.
Ms Gudleifsdóttir posted a new photograph on Flickr to highlight her problem with the gallery and received more than 450 comments of support from other users.
But that post was removed by Flickr staff on the grounds it could "harass, abuse, impersonate, or intimidate others".
Ms Guðleifsdóttir said Flickr had also threatened to terminate her account.
"Freedom of expression? Telling the truth? Not popular with Flickr administration, apparently," she wrote on her blog.
The co-founder of Flickr, Stewart Butterfield, has now apologised.
"We screwed up and for that I take full responsibility," he said.
He added: "It's important to be clear why the photo was deleted: it had nothing to do with a desire to silence Rebekka from calling attention to the outfit which had reportedly sold copies of her photos without knowledge or permission and without compensating her.
"This had nothing to do with fear of a lawsuit, but with deeply held beliefs about the kind of place we want Flickr to be. Unfortunately, those beliefs were misapplied in this case, but we still hold the general principle to be true."
He said Flickr had removed the comments because there was "personal information of the infringing company's owner and suggestions for how best to exact revenge".
Ms Gudleifsdóttir told BBC News that the gallery had told her they had bought the photos from a third party for £3,000 in good faith and had been shown "official looking documents".
"When my lawyer requested that they send a copy of these documents, to prove that this transaction had indeed taken place, we heard no more from them," she said.
"If I had decided to proceed further with this case, my next move would have been to hire a UK-based lawyer to take them to court. I however did not feel able to do this, as I simply don't have the money needed to pay for it."
She said she had been left feeling "extremely frustrated" by the gallery and had been "offended" by Flickr's initial reaction to her protest.
But she said she had now accepted Flickr's apology but would continue to campaign for compensation.
"The fact remains that they made a profit off my work when they had absolutely no right to," she said.