External Ranking Factors(PART 2)

1. Inbound links to a site

An analysis of inbound links to the page being evaluated is one of the key factors in page ranking. This is the only factor that is not controlled by the site owner.
   It is known to all that interesting sites will have more inbound links. This is because owners of other sites on the Internet will tend to have published links to a site if they think it is a worthwhile resource. The search engine will use this inbound link criterion as its evaluation criteria
   Therefore, two main factors influence how pages are stored by the search engine and sorted for display in search results:
    - Relevance, as described in the previous section on internal ranking factors.
    - Number and quality of inbound links, also known as link citation, link popularity or citation index.

2.Link importance (citation index, link popularity)

   By Simply counting the number of inbound links does not give enough information to evaluate a site. It is obvious that a link from www.google.com should mean much more than a link from some homepage like www.hostingcompany.com/~myhomepage.html. You have to take into account link importance as well as number of links.
   Citation index is used to evaluate the number and quality of inbound links to a site.It is a numeric estimate of the popularity of a resource expressed as an absolute value representing page importance. Each search engine uses its own algorithms to estimate a page citation index.
   The absolute citation index value, a scaled citation index is also used sometimes. It indicates the popularity of a page relative to the popularity of other pages on the Internet.
3.Link Text

   The link text of any inbound site link is very important in search result ranking.

E.g www.seo-n-hack.blogspot.com.If the link text contains appropriate keywords, the search engine regards it as an additional and highly significant recommendation that the site actually contains valuable information relevant to the search query.

4.Google Pagerank

   The Google company was the first company to patent the system of taking into account inbound links. The algorithm was named PageRank.

PageRank is estimated separately for each web page and is determined by the PageRank (citation) of other pages referring to it. It is a kind of “virtuous circle.” The main task is to find the criterion that determines page importance. In the case of PageRank, it is the possible frequency of visits to a page.

The PageRank of a specified web page is thus defined as the probability that a user may visit the web page. It follows that, the sum of probabilities for all existing web pages is exactly one because the user is assumed to be visiting at least one Internet page at any given moment.

  You can determine the PageRank value for any web page with the help of the Google ToolBar that shows a PageRank value within the range from 0 to 10. It should be noted that the Google ToolBar does not show the exact PageRank probability value, but the PageRank range a particular site is in. Each range (from 0 to 10) is defined according to a logarithmic scale.

   Here is an example: each page has a real PageRank value known only to Google. To derive a displayed PageRank range for their ToolBar, they use a logarithmic scale as shown in this table
          Real PR                               ToolBar PR
          1-10                                            1
          10-100                                        2
          100-1000                                    3
          1000-10.000                               4
Etc.

   This shows that the PageRank ranges displayed on the Google ToolBar are not all equal. It is easy, for example, to increase PageRank from one to two, while it is much more difficult to increase it from six to seven.

   In practice, PageRank is mainly used for two purposes:

1. Quick check of the sites popularity.

 2. Evaluation of the competitiveness level for a search query is a vital part of seo work.