How Do Search Engines Work?
Search engines help people find relevant information on the Internet.
Major search engines maintain huge databases of web sites that users can
search by typing in specific search words.
Studies have consistently shown that search engines
are the number one or two way that people find websites. Therefore, it is
critically important to build websites that incorporate elements that
achieve a high ranking in search engine listings. According to a survey done
by Georgia Tech this is how people find out about websites:
- Search Engines -- 87%
- Links from other Sites -- 85%
- Printed Media -- 63%
- Word of Mouth -- 58%
- Newsgroups -- 32%
- E-mail -- 32%
- Television -- 32%
- Books -- 28%
Search engines compile their databases with the aid of programs called
"spiders" or "robots". These search engine spiders crawl the Internet from
link to link, identifying web pages and indexing each site they visit. Once
search engine spiders find a web site, they index the content on those
pages, making the URLs available to Internet users. In turn, owners of web
sites submit their URLs to search engines for crawling and, ultimately,
inclusion in their databases. This is known as search engine submission.
When ranking web pages, search engines follow specific criteria, which
may vary from one search engine to another. Naturally, they want to generate
the most popular (or relevant) pages at the top of their list. Search
engines will look at the page's keywords and phrases, content, HTML meta
tags and link popularity, just to name a few, to determine the value of the
web page. Some list the results of a user's search according to which sites
have the most links from other sites - a system known as
link popularity. Other search engines
prioritize results according to the summary information contained on the web
page's
meta tags, and still others look for common
themes used throughout a site. There are many other ways to organize
results, and most search engines use a combination of several of them.
When you use search engines to find something on the Internet, you're
basically asking the search engine to scan its database and match your
keywords and phrases with the content of the URLs they have on file at that
time. Search engine spiders regularly return to the URLs they index to look
for changes. When changes occur, the index is updated to reflect the new
information.
How about Directories?
Directories are often confused with search engines, but actually they're
completely different. Instead of using spiders to crawl the web, directories
such as Yahoo! and Open Directory Project have real people who
review and index their links. They also require web sites to adhere to rigid
guidelines in order to be included in their indexes. As a result,
directories' indexes tend to contain a comparatively small number but
high-quality links.
The factors that influence search engine rankings simply don't apply to
directory rankings. Instead, directory editors look at the quality of a
site: its functionality, content and design. That means that webmasters
hoping to see their sites listed on directories have to use very different
strategies than for search engine placement.
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