Steven A. Ballmer’s stance may force Yahoo’s next chief executive to find another way to revive the company’s profit.

An advertising blitz intended to help Microsoft polish the tarnished brand of its Windows Vista operating system began this week with a head-scratcher of a commercial.

With the stock down, many shareholders are questioning whether Jerry Yang is the right man to lead Yahoo.

Kevin Johnson’s exit comes as Steven A. Ballmer, Microsoft’s chief executive, is shaking up top-level staff in a bid to improve Microsoft’s Internet search and ad business.

Shareholders searching for détente in the battle between Yahoo and Microsoft are unlikely to find it in Microsoft’s new proposal to buy Yahoo’s search business.

As Bill Gates moves on, it will be up to successors to master the Internet’s challenges or see Microsoft’s stature erode.

As Bill Gates moves on, it will be up to his successors to master the challenges of the Internet or watch Microsoft’s wealth and stature in the industry steadily erode.

Since Yahoo went public in 1996, the company has had new owners — its shareholders — but it is unclear whether Jerry Yang, the company’s co-founder and chief executive, knows this.

Microsoft said Sunday that it approached Yahoo with a narrow aim: a collaboration on Internet advertising.

Empirical evidence suggests that Steven A. Ballmer, Microsoft’s chief executive, will not succeed to sustain in the Internet era what his company had attained in the personal computing era.