SAN FRANCISCO - Yahoo Inc. shares shot up 11 percent today as investors took the resignation of CEO Jerry Yang to mean Microsoft Corp. is more likely to make another bid for the ailing Internet company.

Yang’s emotional attachment to the company he co-founded in 1995 is one of the reasons he balked at a $47.5 billion takeover offer from Microsoft six months ago. The same devotion finally led Yang to conclude he should step aside as chief executive, as the company seeks to bolster its depressed stock price and sagging earnings in an economic downturn that might prove even more wrenching than the dot-com bust of eight years ago.