Some search engines, such as Google and Yahoo!, have toolbars and systems like
Google Search History and My Yahoo!, which collect information about a user.
Search engines can also look at recent searches, or what the search process was for
similar users, to help determine what concepts a searcher is looking for and what
documents are most relevant for the user’s needs.
As people use such a system it takes time to build up a search query history and a
click-through profile. That profile could eventually be trusted and used to
• aid in search personalization
• collect user feedback to determine how well an algorithm is working
• help search engines determine if a document is of decent quality (e.g.,
if many users visit a document and then immediately hit the back
button, the search engines may not continue to score that document
well for that query).
I have spoken with some MSN search engineers and examined a video about MSN
search. Both experiences strongly indicated a belief in the importance of user
acceptance. If a high-ranked page never gets clicked on, or if people typically
quickly press the back button, that page may get demoted in the search results for
that query (and possibly related search queries). In some cases, that may also flag a
page or website for manual review.
As people give search engines more feedback and as search engines collect a larger
corpus of data, it will become much harder to rank well using only links. The more
satisfied users are with your site, the better your site will do as search algorithms
continue to advance.
Real-Time versus Prior-to-Query Calculations
In most major search engines, a portion of the relevancy calculations are stored
ahead of time. Some of them are calculated in real time.
Some things that are computationally expensive and slow processes, such as
calculating overall inter-connectivity (Google calls this PageRank), are done ahead
of time.
Many search engines have different data centers, and when updates occur, they roll
from one data center to the next. Data centers are placed throughout the world to
minimize network lag time. Assuming it is not overloaded or down for
maintenance, you will usually get search results from the data centers nearest you.
If those data centers are down or if they are experiencing heavy load, your search
query might be routed to a different data center.