Internet browser pioneer Marc Andreessen, left, and his longtime business partner, Ben Horowitz, in their office in Menlo Park, Calif., in November 2010. The pair co-founded the venture capital firm Andreessen Horowitz, which launched on July 6, 2009. Andreesen co-founded Netscape and led the team responsible for the creation of Mosaic at the National Center for Supercomputing Applications. He has also served as chief technology officer for AOL, after the company acquired Netscape. He has invested in popular Web companies, including Twitter and Digg.