Yahoo co-founder Jerry Yang will donate $75 million to Stanford University, the university from where he graduated and where he and a fellow student by the name of David Filo began working on a directory of Web sites that became one of the Internet"s first big success stories. Stanford said $50 million of the donation will be used to cover the costs of a new environmental studies center scheduled to be completed in December, $5 million will help fund a 120,000-square-foot center for training doctors but it is unclear how the leftover $20 million will be used. At 38, Yang"s stake in Yahoo is currently worth about $1.8 billion.