There’s been a lot of hype recently about Google’s Web History functionality. If you’re not sure what that is, I’ll try an explain:

As a “guest user” of Google (i.e. you’re not signed in with your Google Account credentials), all of the web searches you perform are logged, and stored for a period of 180 days. The click throughs that you make based on these searches to any given website will then affect how that website is placed in your personal SERP (search engine results page) for any related searches. Following the 180 days, old entries are displaced by newer searches More >