(CNN) - More than 300 Vox Media employees staged a walkout on Thursday as staffers and management failed to come to an agreement for a union contract after more than a year of negotiations.
The walkouts affected Vox Media's group of popular websites -- such as Vox, SBNation, The Verge, Eater, Recode, Curbed, and others -- and some were not publishing new content on Thursday.
"Our unit members are taking their sites dark today to show management how important these issues are to us," tweeted the account for the Vox Media Union.
Another tweet included several photos of an empty newsroom with union posters that said "Contract Now!" on walls and computer screens.
Jason Gordon, the director of communications for the Writers Guild of America East, which is representing the staffers, told CNN Business that the walkout was a sign of unity.
"What you are seeing right now is commitment and solidarity between Vox Media employees," Gordon said.
Gordon said that staffers and management still had not come to agreement on four issues: salary minimums; guaranteed annual cost of living increases; severance agreement; and a plan for freelancers and contractors.
Thursday was the last scheduled day of bargaining with management after negotiations began on April 10, 2018, Gordon said.
In a Thursday email sent to staff, Jim Bankoff, chief executive of Vox Media, weighed in on the walkout, saying he was committed to reaching a deal.
"While I'm disappointed that the union chose to take this action in the midst of good faith bargaining, especially as progress was being made, I am still committed to promptly resolving all outstanding issues," Bankoff wrote.
Bankoff said that he had "instructed our bargaining team to ensure that while making ambitious, values-based investments in our people, we don't undermine that goal by spending so far above industry norms that we create an unsustainable environment."
"Of course we need to pay people competitively and fairly to attract the best and keep them (a.k.a. all of you), but we've stopped short of the union's insistence on levels that far exceed industry norms and averages," Bankoff added. "While paying people a lot more than market wages sounds great on the surface, it's not realistic or smart."
Correction: This story has been corrected to note that some of Vox's sites were publishing on Thursday.
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