Tuesday, November 10, 2009

What Is The Better Type of BackLink?

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Sometimes clients ask: why some websites are ranked higher with fewer backlinks? Although, there are many reasons why this can happen, it is also the case that not all backlinks are of equal value.

Posted by randfish on September 10th, 2009 at 1:28 am Link Building, he wrote a thorough explanation about the many ways search engines evaluate the value of links.
Here is a summary of he points. For a more detail discussion, you should visit his blog where he has several good illustrations and graphs.

First, it is good to understand that there is both Page level and Domain level link value.

Search engines have become more and more dependent entire domain matrics, rather than just an individual page. It's why you'll see new pages or those with very few links ranking highly, simply because they're on an important, trusted, well-linked-to domain. This is sometimes referred to as "domain authority" and is viewed as the single largest factor.

#1 - Internal vs. External

When search engines first began valuing links as a way to determine the popularity, importance and relevance of a document, they found the classic citation-based rule that what others say about you is far more important (and trustworthy) than what you say about yourself. Thus, while internal links (links that point from one page on your site to another) do carry some weight; links from external sites matter far more.

This doesn't mean it's not important to have a good internal link structure, or to do all that you can with your internal links (good anchor text, no unnecessary links, etc.), it just means that a site/page's performance is highly dependent on how other sites on the web have cited it.

Matter of fact, one of the most overlooked SEO activity is creating context based internal linking which is an activity you can do yourself.

#2 - Anchor Text

"exact match" anchor text is more beneficial than simply inclusion of the target keywords in an anchor text phrase.

#3 - PageRank

Whether they call it StaticRank (Microsoft's metric), WebRank (Yahoo!'s), PageRank (Google's) or mozRank (Linkscape's), some form of an iterative, Markov-chain based link analysis algorithm is a part of all the engines' ranking systems. PageRank et al. uses the analogy that links are votes and that those pages which have more votes have more influence with the votes they cast.

The nuances of PageRank are well covered in The Professional's Guide to PageRank Optimization. A general understanding is required if you want to be effective:

  1. Every URL is assigned a tiny, innate quantity of PageRank
  2. If there are "n" links on a page, each link passes that page's PageRank divided by "n" (and thus, the more links, the lower the amount of PageRank each one flows)
  3. An iterative calculation that flows juice through the web's entire link graph dozens of times is used to reach the calculations for each URL's ranking score
  4. Representations like those shown in Google's toolbar PageRank or SEOmoz's mozRank on a 0-10 scale are logarithmic (thus, a PageRank/mozRank 4 has 8-10X the link importance than a PR/mR 3)

#4 - TrustRank

The basics of TrustRank are described in this paper from Stanford - Combatting Webspam with TrustRank. The basic tenet of TrustRank is that the web's "good" and "trustworthy" pages tend to be closely linked together, and that spam is much more pervasive outside this "center." Thus, by calculating an iterative, PageRank-like metric that only flows juice from trusted seed sources, a metric like TrustRank can be used to predictively state whether a site/page is likely to be high quality vs. spam. Linkscape uses this intuition to build mozTrust (mT) and Domain mozTrust (DmT). The point being, get links from high trust sites and don't link to potential spam.

#5 - Domain Authority

Though the phrase "domain authority" is often discussed in the SEO world, a formal, universal definition doesn't yet exist. Most practitioners use it to describe a combination of popularity, importance and trustworthiness calculated by the search engines and based largely on link data (though some also feel the engines may use the age of the site here as well).

#6 - Diversity of Sources

No single metric has a more positive a correlation with high rankings than the number of linking root domains. This appears to be both a very hard metric to manipulate for spam (particularly if you need domains of high repute with diverse link profiles of their own) and a metric that indicates true, broad popularity and importance. Having said this, it is far easier (time and money) to get on all pages of a website, then to get on one page of different and unique website. So although having many unique domains link to your website as your primary goal, do not overlook the potential of links from all web pages within the same domain.

#7 - Uniqueness of Source + Target

The engines have a number of ways to judge and predict ownership and relationships between websites. These can include (but are certainly not limited to):

  • A large number of shared, reciprocated links
  • Domain registration data
  • Shared hosting IP address or IP address C-blocks
  • Public acquisition/relationship information
  • Publicized marketing agreements that can be machine-read and interpreted

#8 - Location on the Page

Microsoft was the first engine to reveal public data about their plans to do "block-level" analysis (in an MS Research piece on VIPS - VIsion-based Page Segmentation). Links from the "content" of a piece is most valuable, both from the value the link passes for rankings and, fortuitously, for click-through traffic as well.

Internal links in the footer of web pages may not provide the same beneficial results that those same links will when placed into top/header navigation. One way the engines appear to be fighting pervasive link advertising is by diminishing the value that external links carry from the sidebar or footer of web pages.

#9 - Topical Relevance

There are numerous ways the engines can run topical analysis to determine whether two pages (or sites) cover similar subject matter. Years ago, Google Labs featured an automatic classification tool that could predict, based on a URL, the category and sub-category for virtually any type of content (from medical to real estate, marketing, sports and dozens more). It's possible that engines may use these automated topical-classification systems to identify "neighbourhoods" around particular topics and count links more or less based on attribute.

#10 - Content & Context Assessment

Though topical relevance can provide useful information for engines about linking relationships, it's possible that the content and context of a link may be even more useful in determining the value it should pass from the source to the target. In content/context analysis, the engines attempt to discern, in a machine parse-able way, why a link exists on a page.

#11 - Geographic Location

The geography of a link is highly dependent on the perceived location of its host, but the engines, particularly Google, have been getting increasingly sophisticated about employing data points to pinpoint the location-relevance of a root domain, subdomain or subfolder. These can include:

  • The host IP address location
  • The country-code TLD extension (.de, .co.uk, etc)
  • The language of the content
  • Registration with local search systems and/or regional directories
  • Association with a physical address
  • The geographic location of links to that site/section

Earning links from a page/site targeted to a particular region may help that page (or your entire site) to perform better in that region's searches, eg web design las vegas. Likewise, if your link profile is strongly biased to a particular region, it may be difficult to appear prominently in another, even if other location-identifying data is present (such as hosting IP address, domain extension, etc).

#12 - Use of Rel="Nofollow"

Although in the SEO world it feels like a lifetime ago since nofollow appeared, it's actually only been around since January of 2005, when Google announced it was adopting support for the new HTML tag. Very simply, rel="nofollow", when attached to a link, tells the engines not to ascribe any of the editorial endorsements or "votes" that would boost a page/site's query independent ranking metrics. Today, Linkscape's index notes that approximately 3% of all links on the web are nofollowed, and that of these, more than half are sites using nofollow on internal, rather than external pointing links.

#13 - Link Type

Links can come in a variety of formats. The big three are:

  1. Straight HTML Text Links
  2. Image Links
  3. Javascript Links

It appears that straight, HTML links with standard anchor text pass the most value, followed by image links with keyword-rich alt text and finally, Javascript links (which still aren't universally followed or considered as an endorsement).

#14 - Other Link Targets on the Source Page

When a page links out externally, both the quantity and targets of the other links that exist on that page may be taken into account by the engines when determining how much link juice should pass.

"PageRank"-like algorithms from all the engines divide the amount of juice passed by any given page by the number of links on that page. In addition to this metric, the engines may also consider the quantity of external domains a page points to as a way to judge the quality and value of those endorsements. If, for example, a page links to only a few external resources on a particular topic, spread out amongst the content, that may be perceived differently than a long list of links pointing to many different external sites. One is not necessarily better or worse than the other, but it's possible the engines may pass greater endorsement through one model than another (and could use a system like this to devalue the links sent from what they perceive to be low-value-add directories).

#15 - Domain, Page & Link-Specific Penalties

Search engines apply penalties to sites and pages ranging from the loss of the ability to pass link juice/endorsement all the way up to a full ban from their indices. If a page or site has lost its ability to pass link endorsements, acquiring links from it provides no algorithmic value for search rankings. Be aware that the engines sometimes show penalties publicly (inability to rank for obvious title/URL matches, lowered PageRank scores, etc.) but continue to keep these penalties inconsistent so systemic manipulators can't acquire solid data points about who can gets "hit" vs. not.

#16 - Content/Embed Patterns

As content licensing & distribution, widgets, badges and distributed, embeddable links-in-content become more prevalent across the web, the engines have begun looking for ways to avoid becoming inundated by these tactics. It is likely that content pattern detection and link pattern detection plays a role in how the engines evaluate link diversity and quality. If the search engines see, for example, the same piece of content with the same link across thousands of sites, that may not signal the same level of endorsement that a diversity of unique link types and surrounding content would provide.

#17 - Temporal / Historical Data

Timing and data about the appearance of links is the final point on this checklist. As the engines crawl the web and see patterns about how new sites, new pages and old stalwarts earn links, they can use this data to help fight spam, identify authority and relevance and even deliver greater freshness for pages that are rising quickly in link acquisition.

Any good SEO campaign must include a long term linkback strategy, based on your monthly budget. Although, there is not just one size fits all approach, dont expect to get the same results from doing directory submissions as you would get from well placed context based theme related links from high PR pages, on multiple domains. An experienced search engine expert is capable of evaluating the cost/benefit trade offs that should be evaluated based your competitive landscape.

By: Nick the SEO guy

1 comment:

  1. Great post, Nick. Another thing that should be part of a good SEO campaign is a diverse link profile, you can check out this link http://blog.directorymaximizer.com/2010/02/03/the-importance-of-link-diversity-in-seo/ to learn more about it.

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