Web 2.0 (or Web 2) is an advanced Internet technology and a medium for the blogs, wikis, RSS and so many popular applications. The main goal of Web 2.0 is web creativity, interaction, safe communication, co-operation and increase of efficiency. This new technology brings new cultural and technical community in the web. There are free hosting services in this medium. In this new community and services there is social networking website, video sharing website, wiki, blog, etc.
There is also a technology definition for web 3.0 that involves using a particular database structure that allows the actual data structure to be changed dynamically without having to redefine the database tables. It never caught on because it actually goes agoinst most of the rules for efficient databae design. Web 3.0 is therefore effectively dead.
Any new approach ought therefore to refer to itself as web 4.0