Yahoo CEO Jerry Yang (L) and Microsoft Chairman Bill Gates in a composite image. Microsoft on Friday said it had offered to acquire Yahoo in a proposed cash and stock deal valued at $44.6 billion.

(File/Reuters)

This combination of two photos shows Microsoft founder Bill Gates, left, and Yahoo CEO Jerry Yang. Microsoft Corp. on Friday, Feb. 1, 2008 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.

(AP Photos)

The Yahoo Center office building is seen in Santa Monica, Calif. Friday, Feb. 2, 2008. The Justice Department on Friday said it is 'interested' in reviewing antitrust issues associated with Microsoft Corp.'s nearly $45 billion unsolicited bid for Yahoo Inc. If the deal goes through, analysts expect scrutiny from Congress, Justice and other enforcement agencies, but they say any concerns about search engine or online advertising market power may not be significant enough to stop the transaction.

(AP Photo/Damian Dovarganes)