SEO Help Season | Yahoo Search General Information.

Yahoo cast aside its Google supplied results and rolled out its own search engine in February 2004 and is now perhaps the second largest search engine with an estimated index size of at least 4.5 billion pages and a reported search share of 21.2%.

Yahoo Guidelines
Content which Yahoo says it likes;
Original and unique content of genuine value
Pages designed primarily for humans, with search engine considerations secondary
Hyperlinks intended to help people find interesting, related content, when applicable
Metadata (including title and description) that accurately describes the contents of a web page
Good web design in general
Content which Yahoo says it does not like:
Pages that harm accuracy, diversity or relevance of search results
Pages dedicated to directing the user to another page
Pages that have substantially the same content as other pages
Sites with numerous, unnecessary virtual hostnames
Pages in great quantity, automatically generated or of little value
Pages using methods to artificially inflate search engine ranking
The use of text that is hidden from the user
Pages that give the search engine different content than what the end-user sees
Excessively cross-linking sites to inflate a site's apparent popularity
Pages built primarily for the search engines
Misuse of competitor names
Multiple sites offering the same content
Pages that use excessive pop-ups, interfering with user navigation
Pages that seem deceptive, fraudulent or provide a poor user experience

Yahoo Quirks
Yahoo will spider and index up to 500 kbytes of each page.
Yahoo does read the meta description tag
It has been reported that the signs of a banned site on Yahoo include:
Only the homepage is indexed.
Fewbacklinks are reported to the home page
The homepage will not rank on any terms, including the page title in quotes.

Yahoo Ranking Factors
Yahoos ranking algorithim is similar to that of Google with perhaps a bit less weight given to anchor text and a bit more to onpage factors. Some of the known factors which affect Yahoo rankings are:
Link Popularity Yahoo uses anchor text and link popularity but not with the same emphasis that Google does.
Keyword density is one of Yahoos ranking factors with a 5% to10% range being desirable.
Anchor text links One of the most important ranking factors in Yahoo, they differ from Google in that they seem to give almost all links a similar weighting.
Page titles are an important factor in Yahoo. Yahoo truncates the page title in the SERPs after about 100 characters, but may record more.
Meta description: is used as a ranking factor in Yahoo.
Meta keywords tag is a minor ranking factor in Yahoo,
H tags Words in H tags are given better than average weighting by Yahoo.
alt tags Yahoo records the content of alt tags on images and seems to give them a small amount of ranking weight if they are links.
Searching with Yahoo
site: this allows one to find all documents within a particular domain and all its subdomains. Example: site:yahoo.com

hostname: this allows one to find all documents from a particular host only. Example: hostname:autos.yahoo.com

link: this allows one to find documents that link to a particular url. Note that htp:// must prefix the URL. Example: link:http://autos.yahoo.com/

url: this alllows one to find a specific document in our index. Note that the http:// is required.Example: url:http://edit.autos.yahoo.com/repair/tree/0.html

inurl: this allows one to find a specific keyword as part of indexed urls. Example: inurl:bulgarian

intitle: this allows one to find a specific keyword as part of the indexed titles. Example: intitle:Bulgarian