Yahoo! was founded in 1994 by David Filo

Yahoo! was founded in 1994 by David Filo and Jerry Yang as a directory of
websites. For many years they outsourced their search service to other
providers, but by the end of 2002 they realized the importance and value of
search and started aggressively acquiring search companies.



Overture purchased AllTheWeb and AltaVista. Yahoo! purchased Inktomi (in
December 2002) and then consumed Overture (in July of 2003), and combined the
technologies from the various search companies they bought to make a new search
engine. Yahoo! dumped Google in favor of their own in house technology on
February 17th, 2004.



Yahoo! has a cool Netrospective of their first 10 years, and Bill Slawski posted
a list of many of the companies Yahoo! consumed since Overture.



On Page Content

Yahoo! offers a paid inclusion program, so when Yahoo! Search users click on
high ranked paid inclusion results in the organic search results Yahoo! profits.
In part to make it easy for paid inclusion participants to rank, I believe
Yahoo! places greater weight on on-the-page content than a search engine like
Google does.



Being the #1 content destination site on the web, Yahoo! has a boatload of their
own content which they frequently reference in the search results. Since they
have so much of their own content and make money from some commercial organic
search results it might make sense for them to bias their search results a bit
toward commercial websites.



Using descriptive page titles and page content goes a long way in Yahoo!



In my opinion their results seem to be biased more toward commerce than
informational sites, when compared with Google.



Crawling

Yahoo! is pretty good at crawling sites deeply so long as they have sufficient
link popularity to get all their pages indexed. One note of caution is that
Yahoo! may not want to deeply index sites with many variables in the URL string,
especially since



Yahoo! already has a boatload of their own content they would like to promote
(including verticals like Yahoo! Shopping)

Yahoo! offers paid inclusion, which can help Yahoo! increase revenue by charging
merchants to index some of their deep database contents.

You can use Yahoo! Site Explorer to see how well they are indexing your site and
which sites link at your site.



Query Processing

Certain words in a search query are better at defining the goals of the
searcher. If you search Yahoo! for something like "how to SEO " many of the top
ranked results will have "how to" and "SEO" in the page titles, which might
indicate that Yahoo! puts quite a bit of weight even on common words that occur
in the search query.



Yahoo! seems to be more about text matching when compared to Google, which seems
to be more about concept matching.



Link Reputation

Yahoo! is still fairly easy to manipulate using low to mid quality links and
somewhat to aggressively focused anchor text. Rand Fishken recently posted about
many Technorati pages ranking well for their core terms in Yahoo!. Those pages
primarily have the exact same anchor text in almost all of the links pointing at
them.



Sites with the trust score of Technorati may be able to get away with more
unnatural patterns than most webmasters can, but I have seen sites flamethrown
with poorly mixed anchor text on low quality links, only to see the sites rank
pretty well in Yahoo! quickly.



Page vs Site

A few years ago at a Search Engine Strategies conference Jon Glick stated that
Yahoo! looked at both links to a page and links to a site when determining the
relevancy of a page. Pages on newer sites can still rank well even if their
associated domain does not have much trust built up yet so long as they have
some descriptive inbound links.



Site Age

Yahoo! may place some weight on older sites, but the effect is nowhere near as
pronounced as the effect in Google's SERPs.



It is not unreasonable for new sites to rank in Yahoo! in as little as 2 or 3
months.



Paid Search

Yahoo! prices their ads in an open auction, with the highest bidder ranking the
highest. By early 2007 they aim to make Yahoo! Search Marketing more of a closed
system which factors in clickthrough rate (and other algorithmic factors) into
their ad ranking algorithm.



Yahoo! also offers a paid inclusion program which charges a flat rate per click
to list your site in Yahoo!'s organic search results.



Yahoo! also offers a contextual ad network. The Yahoo! Publisher program does
not have the depth that Google's ad system has, and they seem to be trying to
make up for that by biasing their targeting to more expensive ads, which
generally causes their syndicated ads to have a higher click cost but lower
average clickthrough rate.



Editorial

Yahoo! has many editorial elements to their search product. When a person pays
for Yahoo! Search Submit that content is reviewed to ensure it matches Yahoo!'s
quality guidelines. Sites submitted to the Yahoo! Directory are reviewed for
quality as well.



In addition to those two forms of paid reviews, Yahoo! also frequently reviews
their search results in many industries. For competitive search queries some of
the top search results may be hand coded. If you search for Viagra, for example,
the top 5 listings looked useful, and then I had to scroll down to #82 before I
found another result that wasn't spammy.



Yahoo! also manually reviews some of the spammy categories somewhat frequently
and then reviews other samples of their index. Sometimes you will see a referral
like http://corp.yahoo-inc.com/project/health-blogs/keepers if they reviewed
your site and rated it well.



Sites which have been editorially reviewed and were of decent quality may be
given a small boost in relevancy score. Sites which were reviewed and are of
poor quality may be demoted in relevancy or removed from the search index.



Yahoo! has published their content quality guidelines. Some sites that are
filtered out of search results by automated algorithms may return if the site
cleans up the associated problems, but typically if any engine manually reviews
your site and removes it for spamming you have to clean it up and then plead
your case. You can request to have your domain evaluated for re-inclusion using
this form.



Social Aspects

Yahoo! firmly believes in the human aspect of search. They paid many millions of
dollars to buy Del.icio.us, a social bookmarking site. They also have a similar
product native to Yahoo! called My Yahoo!



Yahoo! has also pushed a question answering service called Yahoo! Answers which
they heavily promote in their search results and throughout their network.
Yahoo! Answers allows anyone to ask or answer questions. Yahoo! is also trying
to mix amateur content from Yahoo! Answers with professionally sourced content
in verticals such as Yahoo! Tech.