Google Web History

Google's has implemented personalization to improve search
results could face some difficulties. Google already uses your
queries, the results you click on, your bookmarks, but this isn't
enough to build a comprehensive profile. People don't search too many
times and, most often, they click on the top search results.

So I think the next step in Google's efforts to tailor the search
results to your preferences is to expand the search history into
something more complex: the web history. Browsing web pages is an
important part of your online activity and there are already
applications like Google Desktop that monitor and index the visited
web pages.

Google Web History is a reality starting today. This replaces the
previous search history service that was limited only to queries and
search results. If you want to add the web pages you visit, you need
to have Google Toolbar with the PageRank feature activated and to
enable web history from http://www.google.co.in/history/welcome?hl=en.