Forum Moderators: DixonJones
That really is "how long is a piece of string" :)
I don't think anyone truly knows how big the web is, never mind what it contains!
You may be better off trying to estimate what genre the web is divided into by usage, rather than content (known and unknown).
Nielsen, Alexa and MetricsMarket are some of the places that will start to answer the usage question.
My guess is that the single most popular usage for the web is to check email;) After that a lot of digging will need to be done.
Alexa lists the top 500 sites (via their traffic rank system), so an estimation can be made of the useage/ genre from these sites. (If their results are reliable, however you have to start somewhere!)
Webfountain sounds interesting. Could it be the heavyweight contender to Google?