Henrik Frystyk Nielsen is a Danish engineer and computer scientist. He is best known for his pioneering work on the World Wide Web and subsequent work on computer network protocols. Nielsen's Web work began at CERN, and shared an office with Håkon Wium Lie, the co-inventor of Cascading Style Sheets. They developed together the Arena web browser. It was at this time he began work with Berners-Lee, and later joined Roy Fielding et al. He joined the staff of W3C in March 1995, and continued work on HTTP and other Web protocol topics such as the Line Mode Browser and libwww. Nielsen was one of the principal authors of the Hypertext Transfer Protocol (HTTP) specifications, published in 1996. He then managed the development of a "next generation" called HTTP 1.1, published in 1999. Nielsen joined the staff of Microsoft in August 1999, and began work on new versions of SOAP. By the end of 2005, the incubation moved into productization as Nielsen and Chrysanthakopoulos joined the newly formed Microsoft Robotics Group. In June 2006 the first version of the Microsoft Robotics Studio shipped to the public. Nielsen is currently the Principal Architect of the Windows Communication Foundation team at Microsoft, working on WebSocket and some other technologies.