Microsoft Corp. has pounced on slumping Internet icon Yahoo Inc. with an unsolicited takeover offer of $44.6 billion in its boldest bid yet to challenge Google Inc.’s dominance of the lucrative online search and advertising markets.

To underscore its resolve, Microsoft is offering a 62 percent premium to Yahoo’s closing stock price Thursday. If the deal is consummated, it would be by far the largest acquisition in Microsoft’s history, eclipsing last year’s $6 billion purchase of online ad service aQuantive.

(Via Yahoo Business and Daring Fireball.)