Marc Lowell Andreessen ( /ænˈdriːsɨn/ an-DREE-sən; born July 9, 1971) is an American entrepreneur, investor, software engineer, and multi-millionaire best known as co-author of Mosaic, the first widely-used web browser, and co-founder of Netscape Communications Corporation. He founded and later sold the software company Opsware to Hewlett-Packard. He is also a co-founder of Ning, a company which provides a platform for social-networking websites. He sits on the board of directors of Facebook, eBay, and HP, among others. Andreessen is a frequent keynote speaker and guest at Silicon Valley conferences. He is one of only six inductees in the World Wide Web Hall of Fame announced at the first international conference on the World Wide Web in 1994.