Once the site has been visited by search engine spiders and placed in the search engine database, search engine determine which site to place on the first page of the search results but the algorithm behind the ranking is unrevealed. The ranking methodology is different for each search engine, and they are continuously refining the approach in their attempt to deliver the most relevant results.

There are various factors that decide a site’s ranking for a specific search term based on the relevance of the site’s content, the depth of content on the site, and the credibility of the site.

Relevance of content: The most prominent factor is the content read by the search engine spider For any given page strongest, there are three forms of content: Visible, Code and Defining.

Visible Content: Content presented in graphics or in Flash can be read by users but not by crawlers, there fore the content should be visible. In addition, the content needs to match what terms people use to search. This might mean including a mixture of acronyms and the definition of those acronyms.

Code Content: This is the HTML code used to create the page. Early in the search engine optimization era, companies could use tags called ‘META’ tags to list relevant keywords. This meant that one could add content invisible to the user, but read by search engines. The obvious potential for abuse led to decreased reliance on these by search engines. Page names, image names, etc are opportunities to add relevant content that can be read by search engine spiders.

Defining Content: The content in the text of a link to a page tells a user and a search engine a lot about the linked page. When you see a link that says “Information for Marketers”, you expect to see content relevant to marketers on the following page. Search Engines apply the same logic, using the text in the link to further define the relevance of the page.

Depth of Content: When a search engine is trying to determine which page/site will provide a searcher with the best answer to their search question, the amount of available content on a site is considered. Again, if you relate to your own information searching habits, you may go to major bookstores like Borders because they have a large selection available to you. For web sites, a search engine spider will collect the amount of content on your page plus the content you link to in determining the depth of content on a site.

Credibility of content: When a search engine ranks a site, the search engine will ‘check the references’ of the site by evaluating the quality and quantity of the links to a site. Links from more credible sites will boost the ranking of a site over a non-linked site with similar content.

Consider how you look for information in the real world. When you ask for advice on where to shop, a doctor to see, a place to vacation, there are people who’s opinion you value more than others, and you likely have an ‘expert’ you turn to depending on the subject.

Links from credible sites can be the hardest to obtain, which is why this criteria is rising in importance. Unethical search firms attempted to exploit this approach by creating ‘Link Farms’ or pages that simply contained links to client sites plus links to other pages also containing links to these client sites, and so on. Search Engines now try to discourage this practice by removing all sites it finds in these link farm pages, or at least not giving these sites credit for those links.