I suspect this is easy, but I don't have the patience to find the
exact right source.  At the end of 2002, how many hours per week did
the mean American spend surfing the web?  Is there a breakdown of what
they were doing with that time?

Notes:
Some studies might discuss "time online" which may include email time
(as opposed to surfing time).  I'd like to get time viewing web pages
NOT doing email.  Any survey that includes breakdowns into categories
of activity (shopping, gaming, entertainment, etc.) would be great.
  
Some studies you might find would be a survey of "web users" defined
in various ways. If so, its important to me to be able to know what
fraction of the population would be defined as a "web user" so that I
could eventually get to a true per-capita number.  That is, if, for
example, in 2002 25% of the population were defined as "web users" and
the survey suggests that "web users" spend 4 hours per week online,
and "non-web users" presumably spend zero, then the average time spent
online is (0.25)(4) = 1 hour/week.

Crucially, I'm looking for a number for LATE 2002 or EARLY 2003.  

THANKS.