Terry Semel has ended his six-year run as Yahoo's chief executive officer and the company's co-founder Jerry Yang will take over from him, the company said.

Semel has been the focus of intense criticism in the past two years due to Yahoo's inability to capitalise as much as expected on the fast growing market for search engine advertising. By contrast, Google has enjoyed eye-popping revenue growth and enviable profits almost exclusively from the search advertising market.

Last week, at Yahoo's annual shareholder meeting, Semel fielded stinging criticism from shareholders in attendance, leading to tense exchanges at times.

Semel resigned from the position as chief executive and chairman he took up in May 2001 and will become non-executive Chairman and serve as advisor to the management team.

Previously, Semel spent 24 years at Warner Bros, where he was chairman and co-chief executive officer. Prior to that, he led Walt Disney's Theatrical Distribution division and CBS' Theatrical Distribution division.

Semel was brought in primarily to create a bridge between the Hollywood entertainment industry and Yahoo, which never happened as originally envisioned, said Gartner analyst, Allen Weiner. "That strategy didn't work," he said.

Because Yang is an engineer who fully understands the internet market and Yahoo's business, Weiner predicts the company troops will rally behind him. "This is a seminal event in the history of Yahoo," Weiner said.

The board of directors appointed Yang, who co-founded the company 12 years ago, as chief executive and Susan Decker, former executive vice president and head of Advertiser and Publisher Group, as the company's president.

This change is something that the market obviously wanted, according to industry analyst Greg Sterling from Sterling Market Intelligence. When he joined Yahoo, Semel helped bring the company back from the brink, but recently he seemed to have lost the magic touch he had earlier.

"If Yahoo had another lacklustre quarter, the chorus of calls for Semel's resignation would have gotten louder. This might be seen as a pre-emptive move by Semel," Sterling said. The question that remains is whether this executive change will have the desired effects, he said.

In a webcast, Semel said he had told the board that he wanted to step back from his executive role "sooner rather than later" and that he and the board agreed this would be a good time for him to step down.

"I've long been talking to the board about the importance of ensuring a smooth succession to Yahoo's senior leadership," Semel said.

Semel expressed full confidence that Yang and Decker are the right people to carry Yahoo "through its multi-year transformation" while acknowledging that the past year has been a difficult one for Yahoo and that no one in Yahoo's management had been satisfied with the company's performance.