From the Pew Internet & American Life Project (PDF)
Surfing the Web has become one of the most popular activities that internet users will do online on a typical day. Some 30% of internet users go online on any given day for no particular reason, just for fun or to pass the time.
This makes the act of hanging out online one of the most popular activities tracked by the Pew Internet & American Life Project and indicates that the online environment is increasingly popular as a place for people to spend their free time. Compared to other online pursuits, the act of surfing for fun now stands only behind sending or receiving email (52% of internet users do this on a typical day) and using a search engine (38% of internet users do this on a typical day), and is in a virtual tie for third with the act of getting news online (31% of internet users do this on a typical day).
In aggregate figures, this development is striking because it represents a significant increase from the number of people who went online just to browse for fun on a typical day at the end of 2004. In a survey in late November 2004, about 25 million people went online on any given day just to browse for fun. In the Pew Internet Project survey in December, 2005, that number had risen to about 40 million people.