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1. Crawling and Indexing
Crawling and indexing the billions of
documents, pages, files, news,
videos and media on the world wide
2. Providing Answers
Search engines have two major functions - crawling & building an
index, and providing answers by calculating relevancy & serving
Providing answers to user queries,
most frequently through lists of
relevant pages, through retrieval and
Imagine the World Wide Web as a network of stops in a big city subway
Each stop is its own unique document (usually a web page, but sometimes a PDF, JPG or other
file). The search engines need a way to “crawl” the entire city and find all the stops along the way,
so they use the best path available – links.
“The link structure of the web serves to bind all of the pages together.”
Through links, search engines’ automated robots, called “crawlers,” or “spiders” can reach the
many billions of interconnected documents.
Once the engines find these pages, they next decipher the code from them and store selected pieces
in massive hard drives, to be recalled later when needed for a search query. To accomplish the
monumental task of holding billions of pages that can be accessed in a fraction of a second, the
search engines have constructed datacenters all over the world.
These monstrous storage facilities hold thousands of machines processing large quantities of
information. After all, when a person performs a search at any of the major engines, they demand
results instantaneously – even a 1 or 2 second delay can cause dissatisfaction, so the engines work
hard to provide answers as fast as possible.
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Search engines are answer machines . When a person looks for something online, it requires the
search engines to scour their corpus of billions of documents and do two things – first, return only
those results that are relevant or useful to the searcher’s query, and second, rank those results in
order of perceived usefulness. It is both “ relevance ” and “ importance ” that the process of SEO
is meant to influence.
To a search engine, relevance means more than simply finding a page with the right words. In the
early days of the web, search engines didn’t go much further than this simplistic step, and their
results suffered as a consequence. Thus, through evolution, smart engineers at the engines devised
better ways to find valuable results that searchers would appreciate and enjoy. Today, 100s of
factors influence relevance, many of which we’ll discuss throughout this guide.
How Do Search Engines Determine Importance?
Currently, the major engines typically interpret importance as popularit y – the more popular a
site, page or document, the more valuable the information contained therein must be. This
assumption has proven fairly successful in practice, as the engines have continued to increase
users’ satisfaction by using metrics that interpret popularity.
Popularity and relevance aren’t determined manually. Instead, the engines craft careful,
mathematical equations – algorithms – to sort the wheat from the chaff and to then rank the
wheat in order of tastiness (or however it is that farmers determine wheat’s value).
These algorithms are often comprised of hundreds of components. In the search marketing field,
we often refer to them as “ranking factors” SEOmoz crafted a resource specifically on this subject –
You can surmise that search engines
believe that Ohio State is the most
relevant and popular page for the
query “Universities” while the result,
Harvard, is less relevant/popular.
or "How Search Marketers Succeed"
The complicated algorithms of search engines may appear at first glance to be impenetrable. The
engines themselves provide little insight into how to achieve better results or garner more traffic.
What information on optimization and best practices that the engines themselves do provide is
listed below:
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Googlers recommend the following to get better rankings in their
search engine:
Make pages primarily for users, not for search engines. Don't
deceive your users or present different content to search engines
than you display to users, which is commonly referred to as
Make a site with a clear hierarchy and text links. Every page
should be reachable from at least one static text link.
Create a useful, information-rich site, and write pages that
clearly and accurately describe your content. Make sure that
your <title> elements and ALT attributes are descriptive and
Use keywords to create descriptive, human friendly URLs.
Provide one version of a URL to reach a document, using 301
redirects or the rel="canonical" element to address duplicate
Bing engineers at Microsoft recommend the following to get better
rankings in their search engine:
Ensure a clean, keyword rich URL structure is in place
Make sure content is not buried inside rich media (Adobe Flash
Player, JavaScript, Ajax) and verify that rich media doesn't hide
links from crawlers.
Create keyword-rich content based on research to match what
users are searching for. Produce fresh content regularly.
Don’t put the text that you want indexed inside images. For
example, if you want your company name or address to be
indexed, make sure it is not displayed inside a company logo.
Over the 15 plus years that web search has existed, search
marketers have found methods to extract information about how
the search engines rank pages. SEOs and marketers use that data
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to help their sites and their clients achieve better positioning.
Surprisingly, the engines support many of these efforts, though the public visibility is frequently
Engine Strategies , Distilled & SEOmoz’s own MozCon attract engineers and representatives
from all of the major engines. Search representatives also assist webmasters by occasionally
participating online in blogs, forums & groups.
There is perhaps no greater tool available to webmasters researching the activities of the engines than the freedom to use the search engines
to perform experiments, test theories and form opinions. It is through this iterative, sometimes painstaking process, that a considerable
amount of knowledge about the functions of the engines has been gleaned.
1. Register a new website with nonsense keywords (e.g.
5. Record the search engines’ activities and the rankings of the
2. Create multiple pages on that website, all targeting a similarly
ludicrous term (e.g. yoogewgally)
6. Make small alterations to the identically targeting pages to
determine what factors might push a result up or down against
its peers
3. Test the use of different placement of text, formatting, use of
keywords, link structures, etc by making the pages as uniform as
possible with only a singular difference
7. Record any results that appear to be effective and re-test on
other domains or with other terms – if several tests consistently
return the same results, chances are you’ve discovered a pattern
that is used by the search engines.
4. Point links at the domain from indexed, well-spidered pages on
other domains
In this test, we started with the hypothesis that a link higher up in a page’s code carries more
weight than a page lower down in the code. We tested this by creating a nonsense domain linking
out to three pages, all carrying the same nonsense word exactly once. After the engines spidered
the pages, we found that the page linked to from the highest link on the home page ranked first.
This process is not alone in helping to educate search marketers.
Competitive intelligence about signals the engines might use and how they might order results is
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