A: San Francisco, California, United States
The first Web 2.0 Conference was held in San Francisco on October 5-7, 2004.
"Web 2.0 is a term describing changing trends in the use of World Wide Web technology and web design that aims to enhance creativity, secure information sharing, collaboration and functionality of the web. Web 2.0 concepts have led to the development and evolution of web-based communities and its hosted services, such as social-networking sites, video sharing sites, wikis, blogs, and folksonomies. The term became notable after the first O'Reilly Media Web 2.0 conference in 2004. Although the term suggests a new version of the World Wide Web, it does not refer to an update to any technical specifications, but to changes in the ways software developers and end-users utilize the Web. . . .
Some technology experts, notably Tim Berners-Lee, have questioned whether one can use the term in any meaningful way, since many of the technology components of "Web 2.0" have existed since the early days of the Web."