According to Matt Cutts at Google, there are some 200 variables in the Google Algorithm. Each factor unto itself is less than the sum of the parts. The key idea is to efficiently compute for each sensor an estimate of the probability that it matches the query and process sensors in the order of decreasing probability, such that effort is first spent on sensors that are very likely to actually match the query.
Another class of techniques and sensors, known as black hat SEO or spamdexing, use methods such as link farms, keyword stuffing and article spinning that degrade both the relevance of search results and the user-experience of search engines. Search engines look for sites that employ these techniques in order to remove them from their indices. What should be noted, techniques considered acceptable today may be viewed upon with disdain going forward.
Google makes note in its Quality Guidelines, using off-the-shelf software can lead to detrimental results in your rankings.
Increasing prominence
A variety of other methods are employed to get a web page shown at the top of search results. These include:
Cross linking between pages of the same website. Giving more links to main pages of the website, to increase PageRank used by search engines. Linking from other websites, including link farming and comment spam. Writing content that includes frequently searched keyword phrase, so as to be relevant to a wide variety of search queries. Adding relevant keywords to a web page meta tags, including keyword stuffing. URL normalization of web pages accessible via multiple urls, using the “canonical” meta tags.
Domain
– Age of Domain
– History of domain
– KWs in domain name
– Sub domain or root domain?
– TLD of Domain
– IP address of domain
– Location of IP address / Server
Architecture
– HTML structure
– Use of Headers tags
– URL path
– Use of external CSS / JS files
Content
– Keyword density of page
– Keyword in Title Tag
– Keyword in Meta Description (Not Meta Keywords)
– Keyword in KW in header tags (H1, H2 etc)
– Keyword in body text
– Freshness of Content
Per Inbound Link
– Quality of website linking in
– Quality of web page linking in
– Age of website
– Age of web page
– Relevancy of page’s content
– Location of link (Footer, Navigation, Body text)
– Anchor text if link
– Title attribute of link
– Alt tag of images linking
– Country specific TLD domain
– Authority TLD (.edu, .gov)
– Location of server
– Authority Link (CNN, BBC, etc)
Cluster of Links
– Uniqueness of Class C address.
Internal Cross Linking
– Number of internal links to page
– Location of link on page
– Anchor text of FIRST text link
Penalties
– Over Optimization
– Purchasing Links
– Selling Links
-Links from Web Spam sites
-frequent server down time
– Comment Spamming
– Cloaking
Cloaking by cookie detection
Cloaking by JavaScript
Cloaking by rich media support
Cloaking by IP address
Cloaking by User Agent
– Hidden Text
– Duplicate Content
– Keyword stuffing
– Manual penalties
– Sandbox effect
Miscellaneous
– JavaScript Links
– No Follow Links
Pending
– Performance / Load of a website
– Speed of JavaScript
Misconceptions
– XML Sitemap (Aids the crawler but doesn’t help rankings)
– PageRank (General Indicator of page’s performance)