Yahoo has announced that chairman Fred Amoroso is resigning from the post, effective immediately, and will not seek re-election to the board of directors in June.
The role of chairman will be taken over by Yahoo director Maynard Webb until the company's annual shareholder meeting on 25 June.
"Fred has been a wonderful chairman for Yahoo over the past year, and I'm personally grateful for his trust and guidance as I took on the role as chief executive,” said CEO Marissa Mayer.
"Fred's mentorship and perspective has proved truly valuable to me in my first few months here at Yahoo," she said in a statement.
Amoroso said he was proud of the progress the internet firm has made in the past year.
"When I took the position as chairman, I told the board that my intention was to serve for one year, to help Yahoo during a critical time of transformation,” he said.
Amoroso said in that time the company had “hired a great new CEO, brought on a fantastic management team, revitalised the employee base, and has begun to release top notch new products.
“With Marissa at the helm and the leadership team in place, this is a natural time for me to transition off the board, consistent with what I said a year ago,” he said.
Following the completion of Amoroso's term at the annual meeting, the board will comprise 10 members.
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Yahoo shares, which have risen roughly 60% since Mayer became CEO, were down eight cents to $25.12 in after-hours trading on Thursday 25 April, according to Reuters.
Yahoo has seen its revenue stall in recent years in the face of competition from Google and Facebook.
Earlier this month, Mayer tried to put a positive spin on the company’s lacklustre first quarter results, which saw revenues of $1.14bn, down 7% from the same period a year ago.
Mayer said she was pleased with Yahoo’s performance and said the company had seen continued stability in the first three months of the year.
"We are moving quickly to roll out beautifully designed, more intuitive experiences for our users. I'm confident that the improvements we're making to our products will set up the company for long-term growth," she said.
Income from operations increased 10% to $186m, compared with the first quarter of 2012; net earnings were $390m, up 36%; and net earnings per diluted share were $0.35, compared with $0.23 in 2012.
However, display revenue was $455m, an 11% decrease compared with $511m for the first quarter of 2012, and search revenue was down 10% to $425m.
Mayer, who has been entrusted with turning the company around in the face of competition from Google, has been trying to make Yahoo's online services more compelling to boost advertising sales.