One of the most common questions related to Google search is “How does Google decide what result goes at the top of the list?” Google quality engineer Matt Cutts, shows how Google crawls and indexes the web and then ranks search results. This article is worth reading if you really wanna know why Google is so relevant unlike its peers like MSN or Yahoo!

An interesting excerpt from the article:

Once we’ve built our index, we’re ready to rank documents and determine how relevant they are. Suppose someone comes to Google and types in civil war. In order to present and score the results, we need to do two things:

We’ve developed an interesting trick that speeds up the first step: instead of storing the entire index on one very powerful computer, Google uses hundreds of computers to do the job. Because the task is divided among many machines, the answer can be found much faster. To illustrate, let’s suppose an index for a book was 30 pages long. If one person had to search for several pieces of information in the index, it would take at least several seconds for each search. But what if you gave each page of the index to a different person? Thirty people could search their portions of the index much more quickly than one person could search the entire index alone. Similarly, Google splits its data between many machines to find matching documents faster.

How does Google collect and rank results?