Search engine ranking factor survey data has shown that getting external links is the single most important target for achieving high rankings. This is because of the idea that external links are one of the most difficult ways to manipulate and thus one of the best ways for search engines to determine the popularity of a particular web page. This idea ( Link Building ) was first used by the early search engine Alta Vista and later enhanced by Google.
The search engines use many measurement methods to determine the value of external links. Read more
The number of links to the same page on the source page.
The number of root domains that link to the landing page.
The number of variants used as anchor text links to the landing page.
The ownership relationship between the source and target domains.
Used by search engines
How do search engines assign the value to links? To answer this, we need to examine the individual elements of a link and look at how search engines assess these elements.
We do not really understand the own measurements that search engines use, but through analysis of patent applications, experience, and link building tests, we can draw some intelligent assumptions that hold the real world. Here is a list of notable factors worth considering.
These signals, and many more are considered by professional search engine optimizers at measurement link value and a website link profile.
The more popular and important the site is, the more links from the site matter. A site like Wikipedia has thousands of different sites linking to it, which means it’s probably a popular and important site.
In order to earn trust and authority with the engines, you need the help of other link partners. The more popular, the better.
Local Topic Specific Popularity
The term “local” popularity, search engine, indicates that links from sites within a subject-specific society matter more than links from public or off-topic sites.
For example, if your website sells (shirts), a link from Society of (Clothing) means much more than one from a website about roller skates.
One of the strongest signals the engines use in the ranking is anchor text. If dozens of links point to a page with the right keywords, that page has a very good likelihood of ranking well-targeted phrase to anchor text.
You can see examples of this in action with searches like “click here”, where many results rank only because of anchor text of incoming links.
It is no surprise that the Internet contains large amounts of spam. An estimate as much as 60% of the pages are spam. To expose this irrelevant content, search engines use systems to measure trust, many of which are based on the link graph.
Serving links from highly trusted domains can lead to a sharp boost for this point metric. University, government websites, and nonprofit organizations represent examples of high-confidence domains.
Spam links often go in both directions. A site that links to spam is probably spam itself and, in turn, often has many spam sites that link back to it.
By looking at these links in the aggregate, search engines can understand the “Link Neighborhood” link building where your website is located. Therefore, it is wise to choose the sites you’re linking to carefully and be as selective with the sites you try to earn links from.
Linking tones tend to decay over time. Places that once were popular often go unkind, and eventually fail to earn new links.
Therefore, it is important to continue earning additional links over time. Commonly called “FreshRank” search engines use freshness signals links to assess current popularity and relevance.
The last few years have seen an explosion in the amount of content shared through social services such as Facebook, Twitter and Google+. Even search engines treat socially shared links differently than other types of links, they still notice them.
There is a lot of debate among search engine professionals about how exact search engines factor social link signals in their algorithms, but it is not possible to deny the increasing importance of social channels.