Marc Andreessen is an American venture capitalist. He started his career as a software engineer and coauthored Mosaic, the first web browser. He co-founded Netscape Communications, which produced one of the first popular commercial browsers, Ning, a social networking service, and Opsware, which was sold to Hewlett Packard. He is a board member of Facebook, Ebay and Hewlett Packard. In 2009 he co-founded the venture capital firm Andreessen Horowitz with Ben Horowitz.