Link farm
Online Advertising
Link farm
On the
World Wide Web, a link farm is any group of web pages that all
hyperlink to every other page in the group. Although some link farms
can be created by hand, most are created through automated programs and
services. A link farm is a form of
spamming the index of a
search engine (sometimes called
spamdexing).
History
Link farms were developed by
search engine optimizers in 1999 to take advantage of the Inktomi search engine's dependence upon link popularity. Although link popularity is
used by some search engines to help establish a ranking order for search
results, the Inktomi engine at the time maintained two indexes. Search results
were produced from the primary index which was limited to approximately
100,000,000 listings. Pages with few inbound links continually fell out of the
Inktomi index on a monthly basis.
Inktomi was targeted for manipulation through link farms because it was then
used by several independent but popular search engines, such as HotBot. Yahoo!,
then the most popular search service, also used Inktomi results to supplement its directory search feature. The link farms helped
stabilize listings for (normally) online business Web sites that had few natural
links from larger more stable sites in the Inktomi index.
Link farm exchanges were at first handled on an informal basis, but several
service companies were founded to provide automated registration,
categorization, and link page updates to member Web sites.
When the Google
search engine became popular, search engine optimizers learned that Google's
ranking algorithm depended in part on a link weighting scheme called
PageRank.
Rather than simply count all inbound links equally, the
PageRank
algorithm determines that some links may be more valuable than others, and
therefore assigns them more weight than others. Link farming was adapted to help
increase the PageRank of member pages.
However, even the link farms became susceptible to manipulation by
unscrupulous Webmasters who joined the services, received inbound linkage, and
then found ways to hide their outbound links or to avoid posting any links on
their sites at all. Link farm managers had to implement quality controls and
monitor member compliance with their rules to ensure fairness.
Alternative link farm products emerged, particularly link-finding software
that identified potential reciprocal link partners, sent them template-based
emails offering to exchange links, and create directory-like link pages for Web
sites hoping to build their link popularity and PageRank.
Search engines countered the link farm movement by identifying specific
attributes associated with link farm pages and filtering those pages from
indexing and search results. In some cases, entire domains were removed from the
search engine indexes in order to prevent them from influencing search results.
Justification
The justification for link farm-influenced crawling diminished
proportionately as the search engines expanded their capacities to index more
sites. Once the 500,000,000 listing threshold was crossed, link farms became
unnecessary for helping sites stay in primary indexes. Inktomi's technology, now
a part of Yahoo!, now indexes billions of Web pages and uses them to offer its
search results.
Where link weighting is still believed by some Webmasters to influence search
engine results with Google, Yahoo!,
MSN, and Ask (among others),
link farms remain a popular tool for increasing PageRank or perceived equivalent
values. PageRank-like measurements apply only to the individual pages being
linked to (typically the reciprocal linking pages on member sites), so these
pages must in turn link out to other pages (such as the main index pages of the
member sites) in order for the link weighting to help.
The expression "link farm" is now considered to be
pejorative and derogatory. Many reciprocal link management service operators tout the value
of their resource management and direct networking relationship building. The
reciprocal link management services promote their industry as an alternative to
search engines for finding and attracting visitors to Web sites. Their
acceptance is by no means universal but the link management services seem to
have established a stable customer base.
Guidelines
Google indicates in its Webmaster Guidelines that more than 100 factors are
used to determine search results rankings. There is considerable debate in the
search engine optimization community regarding the continued value of PageRank.
Mike Grehan, a well-known search engine optimization columnist, has publicly
quoted engineers from Yahoo! and Ask who say Google never fully implemented
their PageRank algorithm.
Search engines such as Google recommend that webmasters request relevant links to their sites (conduct a
link
campaign), but avoid participating in link farms. According to Google, a
site that participates in a link farm may have its
search rankings penalized.
Search engines try to identify specific attributes associated with link farm
pages and filter those pages from indexing and search results. In some cases,
entire domains are removed from the search engine indexes in order to prevent
them from influencing search results.
See also
External links
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