Prism and privacy: What could they know about me? [View all]

This article applies in Britain and to some extent here.

When you visit a website, your IP address, type of machine and screen size can easily be ascertained.

The website can also see how you got to the site - by what search term or the last website you were on. Your location can be found by cross-referring your IP address with other data.

. . . .
A user's IP address on a personal computer can change regularly, he says. For this reason, most companies will only use the IP address to get a vague idea of where their visitors are coming from.

In theory internet service providers (ISPs) can "see" everything a user chooses to do online including every website they visit. But BT, one of the biggest British ISPs, says: "In terms of internet usage BT doesn't keep a record of any of our customers' browsing activity as we have no business need for this."

http://www.bbc.co.uk/news/magazine-22853432

The article is quite interesting and describes the data collected on us throughout our internet activities and daily lives. You will know a lot of it, but the article points out the limitations on learning about a person from their internet browsing as well as what can be discovered about us.