This document summarizes 17 factors that search engines use to determine the value of a link when evaluating websites for ranking. It begins by explaining the importance of external links over internal links. It then lists factors like anchor text, PageRank, the page or domain authority of the linking page, and TrustRank - whether the linking page is considered a good or spammy site. The document provides details on each factor and how they influence search engine rankings.

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17 Ways Search Engines Judge the Value of a Link Navigation
Posted by randfish on September 10th, 2009 at 1:28 am Link Building
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As you've likely noticed, search engines have become more and more dependent on metrics about an entire
domain, 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 ­linked­to domain. In the ranking factors survey,
we called this "domain authority" and it accounted for the single largest chunk of the Google algorithm (in the
aggregate of the voters' opinions). Domain authority is likely calculated off the domain link graph, which is
unique from the web's page­based link graph (upon which Google's original PageRank algorithm is based). In
the list below, some metrics influence only one of these, while others can affect both.
#1 ­ Internal vs. External

2. aggregate of the voters' opinions). Domain authority is likely calculated off the domain link graph, which is
unique from the web's page­based link graph (upon which Google's original PageRank algorithm is based). In
the list below, some metrics influence only one of these, while others can affect both.
#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 citation­based 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 dependant on how other sites on the web have cited it.
#2 ­ Anchor Text
An obvious one for those in the SEO business, anchor text is one of the biggest factors in the rankings
equation overall, so it's no surprise it features prominently in the attributes of a link that engines consider.

3. An obvious one for those in the SEO business, anchor text is one of the biggest factors in the rankings
equation overall, so it's no surprise it features prominently in the attributes of a link that engines consider.
In our experiments (and from lots of experience), it appears that "exact match" anchor text is more beneficial
than simply inclusion of the target keywords in an anchor text phrase. On a personal note, it's my opinion
that the engines won't always bias in this fashion; it seems to me that, particularly for generic (non­branded)
keyword phrases, this is the cause of a lot of manipulation and abuse in the SERPs.
#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, Markov­chain 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, but, at a
minimum, understanding of the general concepts is critical to being an effective SEO:
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 8­10X the link importance than a
PR/mR 3)
PageRank can be calculated on the page­level link graph, assigning PageRank scores to individual URLs, but
it can also apply to the domain­level link graph, which is how metrics like Domain mozRank (DmR) are
derived. By counting only links between domains (and, to make a crude analogy, squishing together all of the
pages on a site into a single list of all the unique domains that site points to), Domain mozRank (and the
search engine equivalents) can be used to determine the importance of an entire site (which is likely to be at
least a piece of how overall domain authority is generated).
#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

4. search engine equivalents) can be used to determine the importance of an entire site (which is likely to be at
least a piece of how overall domain authority is generated).
#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,
PageRank­like 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.
While the engines don't expose any data points around this particular metric, it's likely that some form of the
"distance from trusted seeds" logic is applied by ranking algorithms. Another interesting point on TrustRank ­
Reverse TrustRank, which measures who links to known spam sites, is likely also part of the engines'
metrics set. As with PageRank (above), TrustRank (and Reverse TrustRank) can be calculated on both the
page­level and domain­level link graph. Linkscape uses this intuition to build mozTrust (mT) and Domain
mozTrust (DmT), though our team feels that we still have a lot of work to do in refining these metrics for the
future.
The key takeaways are fairly intuitive ­ 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).
Search engines likely use scores about the "authority" of a domain in counting links, and thus, despite the
fuzzy language, it's worth mentioning as a data point. The domains you earn links from are, potentially, just
as important (or possibly more important) than the individual metrics of the page passing the link.
#6 ­ Diversity of Sources
In our analysis of correlation data, 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. You can see a list of top pages and top domains on the web
ordered by the number of unique root domains with links to them via Linkscape's Top 500.
Although correlation is not causation, the experience of many SEOs along with empirical data suggests that
a diversity of domains linking to your site/page has a strong positive effect on rankings. By this logic, it
follows that earning a link from a site that's already linked to you in the past is not as valuable as getting a
link from an entirely unique domain. This also suggests that, potentially, links from sites and pages who have
themselves earned diverse link profiles, may be more trusted and more valuable than those from low diversity
sources.
#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):
l A large number of shared, reciprocated links
l Domain registration data
l Shared hosting IP address or IP address C­blocks
l Public acquisition/relationship information

5. These can include (but are certainly not limited to):
l A large number of shared, reciprocated links
l Domain registration data
l Shared hosting IP address or IP address C­blocks
l Public acquisition/relationship information
l Publicized marketing agreements that can be machine­read and interpreted
If the engines determine that a pre­existing relationship of some kind could inhibit the "editorial" quality of a
link passing between two sites, they may choose to discount or even ignore these. Anecdotal evidence that
links shared between "networks" of websites pass little value (particularly the classic SEO strategy of
"sitewide" links) is one point many in the organic search field point to on this topic.
#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 ­ VIsion­based Page Segmentation).
Since then, many SEOs have reported observing the impact of analysis like this from Google & Yahoo! as
well. It appears to us at SEOmoz, for example, that 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. Others have
reported that 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.
SEOs tend to agree on one point ­ that links from the "content" of a piece is most valuable, both from the
value the link passes for rankings and, fortuitously, for click­through traffic as well.
#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 sub­category 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 the behaviour they see as accretive to their quality of ranking results.
I personally don't worry too much about topical relevance ­ if you can get a link from a topic agnostic site (like
NYTimes.com) or a very specific blog on a completely unrelated subject (maybe because they happen to like
something you published), I'm bullish that these "non­topic­specific" endorsements are likely to still pass
positive value. I think it's somewhat more likely that the engines might evaluate potential spam or
manipulative links based on these analyses. A site that's never previously linked ­to pharmaceutical, gambling
or adult topic regions may appear as an outlier on the link graph in potential spam scenarios.
#10 ­ Content & Context Assessment

6. or adult topic regions may appear as an outlier on the link graph in potential spam scenarios.
#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 parse­able
way, why a link exists on a page.
When links are meant editorially, certain patterns arise. They tend to be embedded in the content, link to
relevant sources, use accepted norms for HTML structure, word usage, phrasing, language, etc. Through
detailed pattern­matching and, potentially, machine learning on large data sets, the engines may be able to
form distinctions about what constitutes a "legitimate" and "editorially ­given" link that's intended as an
endorsement vs. those that may be placed surreptitiously (through hacking), those that are the result of
content licensing (but carry little other weight), those that are pay­for­placement, etc.
#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:
l The host IP address location
l The country­code TLD extension (.de, .co.uk, etc)
l The language of the content
l Registration with local search systems and/or regional directories
l Association with a physical address
l 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. Likewise, if your link profile is strongly biased to a particular region,
it may be difficult to appear prominently in another, even if other location­identifying 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.

7. "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.
Some question exists in the SEO field as to whether, and how strictly, each individual engine follows this
protocol. It's often been purported, for example, that Google may still pass some citation quality through
Wikipedia's external links, despite the use of nofollow.
#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
Google recently announced that they're not only crawling this third group, but passing link endorsement
metrics through them (which has many upset about the reversal in policy about using Javascript as a way to
delineate paid/advertising links). For years now, they've also treated the text in an image's alt attribute in a
similar fashion to how anchor text is handled in standard text links.
However, not all links are treated equally. In both anecdotal examples and testing, it appears that straight,
HTML links with standard anchor text pass the most value, followed by image links with keyword­rich alt text
and finally, Javascript links (which still aren't universally followed or considered as an endorsement, at least
in our experience). Link builders, content licensers, badge and widget creators and those who enable
embeddable content should all, in my opinion, assume the worst about the engines' ability to handle and
pass value from non­standard links and aim to get HTML text links with good anchor text as an optimal
methodology.
#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.
As we've already mentioned above (in item #3), the "PageRank"­like algorithms from all the engines (and
SEOmoz's mozRank) 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).

8. 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).
The engines are also very likely to be looking at who else a linking page endorses. Having a link from a page
that also links to low quality pages that may be considered spam is almost certainly less valuable than
receiving links from pages that endorse and link out to high quality, reputable domains and URLs.
#15 ­ Domain, Page & Link­Specific Penalties
As nearly everyone in the SEO business is aware (though those in the tech media may still be a bit behind),
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 links­in­content become
more prevalent across the web, the engines have begun looking for ways to avoid becoming inundated by
these tactics. I don't believe that the engines don't want to count the vast majority of links that employ these
systems, but they're also wary about over­counting or over­representing sites that simply do a good job
getting distribution of a single badge/widget/embed/licensing­deal.
To that end, here at SEOmoz, we think it's 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. The "editorial"
nature of a highly similar snippet compared to those of clearly unique, self­generated links may be debatable,
but from the engines' perspectives, being able to identify and potentially filter links using these attributes is a
smart way to future­proof against manipulation.
#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.
How the engines use these patterns of link attraction is up for debate and speculation, but the data is almost
certainly being consumed, processed and exploited to help ranking algorithms do a better job of surfacing the
best possible results (and reducing the abilities of spam ­ especially large link purchases or exploits ­ to have
an impact on the rankings).
While the list above includes many data points, it's almost certainly not comprehensive. Please feel free to
suggest others that belong here in the comments below.
Do you like this post? 48
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User Comments Add Comment Hide Comments
Michael
Sparer September 10th, 2009 at 1:59 am
I'd really like to know how long #11 (Geographic location) based on the
server's IP address will be important for search rankings. As more and more
webapplications move into "the cloud" and thus getting IPs from ranges of big
cloud providers such as amazon, which are mainly hosted in the US or UK, I
don't think that GYM will put much weight on it in the future.

9. Michael
Sparer September 10th, 2009 at 1:59 am
I'd really like to know how long #11 (Geographic location) based on the
server's IP address will be important for search rankings. As more and more
webapplications move into "the cloud" and thus getting IPs from ranges of big
cloud providers such as amazon, which are mainly hosted in the US or UK, I
don't think that GYM will put much weight on it in the future.
Furthermore the trend seems to go into mirroring the content to various
locations spread around the globe (such as amazon's cloud front does) which
then serve the content based on the vicinity of the client's IPs, resulting in
faster response times and a faster web experience for users ... and that's one
of google's current incentives isn't it (e.g. PageSpeed)?
By the way I posted a question to Matt Cutts on the google moderator page
about exactly that IP address / cloud problem ... but didn't get an answer yet.
If you're interested, maybe it'll help if you vote it up : ­)
3 up, 0 down
Reply Permalink
mnnorge
September 10th, 2009 at 2:10 am
Very interesting topic Rand Fishkin. This blog post will be sent to all our SEOs
and memorized.
1 up, 0 down
Reply Permalink
Mikkel deMib
Svendsen September 10th, 2009 at 2:36 am
Just a small correction to #12 ... rel=NOFOLLOW is not really a new HTML­tag
but rather a new attribute value. rel= is not new ­ only the NOFOLLOW value :)
4 up, 0 down
Reply Permalink
twentysix Search
September 10th, 2009 at 3:09 am
Absolutely. I know how annoying it is to constantly correct / be corrected on precise
terminology, but I think it's equally important that in an industry which is so segmented
between SEOs, developers, socials, marketers, designers etc, that we're as absolutely
clear and consistant with our use of terminology as possible in order to minimise the
already extensive amounts of confusion that exist in communicating cross ­
department/expertise...
Edited by twentysix Search on September 10th, 2009 at 3:10 am
1 up, 0 down
Reply Permalink
umseo
September 10th, 2009 at 2:54 am
Great article. It covers pretty much all aspects of links in SEO.
1 up, 0 down
Reply Permalink
davidodonnell
September 10th, 2009 at 3:17 am
Great resource for training link builders.
Props to whatever/whoever you use for creating graphics. Illustrating the point
really helps when explaining link value concepts.
Edited by davidodonnell on September 10th, 2009 at 3:19 am
2 up, 0 down
Reply Permalink

10. really helps when explaining link value concepts.
Edited by davidodonnell on September 10th, 2009 at 3:19 am
2 up, 0 down
Reply Permalink
philou2803
September 10th, 2009 at 3:44 am
That's a great long post Rand. Well done for this one.
I agree with you about the anchior text policy. Search engines could change the
way they look at it. I think Exact Match anchor text does not look natural.
1 up, 0 down
Reply Permalink
Springboard
SEO September 10th, 2009 at 3:46 am
Sweet write up Rand! (How original, I know...)
Thorough resource pages like this one are so handy in catching some of the
obvious­yet­easy ­to­forget optimization factors.
I wrote a page on measuring quality backlinks last month, in which I added
Mozrank and Trustrank to the list of important factors determining link quality.
Seems I forgot to mention 'geographic location', 'link types', and 'other link
targets', though :o
Thanks!
Edited by Springboard SEO on September 10th, 2009 at 4:30 am
1 up, 1 down
Reply Permalink
adders
September 10th, 2009 at 3:54 am
If someone had asked me how many different ways there was for a search
engine to look at a link I'm pretty sure I would have given a number way lower
than 17!
Although I guess it all depends how you break it down.
Really useful break down though :) thumbs ^
1 up, 0 down
Reply Permalink
Neyne
September 10th, 2009 at 4:47 am
Hey Rand,
Great roundup.
Just to add a bit more to the point you made at the end of the #12 point, it is
not true that Google will not pass any link metrics through a nofollowed link.
In an experiment I performed with two links pointing to the same target from
the same page, the first link passed anchor text even when nofollowed.
I wrote more about it here: http://www.seo­scientist.com/first­link­counted­
rebunked.html
Cheers
Branko
Edited by Neyne on September 10th, 2009 at 4:57 am
2 up, 1 down
Reply Permalink

11. Edited by Neyne on September 10th, 2009 at 4:57 am
2 up, 1 down
Reply Permalink
James Lowery
September 10th, 2009 at 6:52 am
rel="nofollow" links show up in the back link information in GWT, and Googlebot does
appear to follow this type of link to discover new information.
To my mind, nofollow is a bit of a misnomer, perhaps rel="nocount" or rel="novalue"
would have been more accurate names.
1 up, 0 down
Reply Permalink
Robert
Enriquez September 10th, 2009 at 4:59 am
Exatch match is the way to go most of the times.
Google loves exact match domains, and they also love exact match anchor
text.
1 up, 0 down
Reply Permalink
Springboard SEO
September 10th, 2009 at 5:23 am
I find exact match domaining to be less effective that it was, say 3 years ago.
In fact, I had an exact match domain for my main SEO site until June, at which point I
moved to a more brandable "half ­match" domain. I'm doing better on local rankings since
removing half of the exact ­match equation.
Even if exact matches did provide the same edge rank ­wise as they did a few years ago,
I'd still opt for an extra layer of brandability over a couple of spots on the SERPs.
1 up, 0 down
Reply Permalink
Robert Enriquez
September 10th, 2009 at 6:08 am
I have used and still use exact match for highly competitive commercial terms.
They still rank on page 1 with little work on and off page.
They're also a 2nd part of getting another domain on page 1 of Google. Great 2nd
strategy that helps out in a lot of ways.
1 up, 0 down
Reply Permalink
SEO­Doctor
September 10th, 2009 at 5:26 am
Isn't #4 & #5 the same thing? Domain Authority and Trust. This ones gonna
need a few re ­reads to get the most out of it.
1 up, 0 down
Reply Permalink
goodnewscowboy

12. Reply Permalink
goodnewscowboy
September 10th, 2009 at 5:36 am
Hey Rand. Another crystal clear post that's getting printed out.
Honestly, between products like Linkscape and articles like this, you should be
registering the name LINKmoz.org.
The information that's available here at SEOmoz has been getting better and
better, and I find myself marking many of the other RSS feeds I used to read
regularly as read without actually reading them. I'm finding more and more
substance from SEOmoz, and more and more fluff elsewhere.
I'm really gonna have to break down one of these days and reclaim my pro
membership...
1 up, 0 down
Reply Permalink
gohewitt
September 10th, 2009 at 5:52 am
Absolutely one of the greatest SEO posts Ive ever read! Thank you for this
outstanding information, I feel like I just learned about 5 new things that I had
never thought of before! You guys are like the kings of SEO!
1 up, 0 down
Reply Permalink
BarryB
September 10th, 2009 at 6:18 am
Great information. We have been working with exact match as well while
changing it up once in a while to "look" natural butwondering if we are diluting
the overall link profile of the page.
1 up, 0 down
Reply Permalink
The Perfect
Wedding September 10th, 2009 at 6:29 am
Guys I have one question that keeps stricking me every time I talk with people
about PR referred to in #3
Does a pagina lose PR if they link out to other sources? Cause if something
flows, something is going out/away.
Or is the page keeping it's strength? and only the specific links have a
dampening­factor?
2 up, 0 down
Reply Permalink
nicchenet
September 10th, 2009 at 6:43 am
There's a lot of buzz about whether or not it is a bad idea to post external links on your
website, Wedding. My feeling is that linking to certain external sites with authoritative
qualities [i.e. a .gov website or a .edu that is topically relevant to my website] may
actually give MY site a boost in PR, mozTrust, etc. Of course, I go back and forth on this
issue, but for the most part, I no longer see a need to nofollow all external links ­ there's
value in building a relationship with authoritative sites in my niche.
1 up, 0 down
Reply Permalink
Steph Woods

13. 1 up, 0 down
Reply Permalink
Steph Woods
September 10th, 2009 at 12:04 pm
I agree with nichenet. Linking out to other authoratative (and relevant) sites reflects
positively on your own site.
I also believe that external linking shows the search engines that you are
attempting to provide readers with valuable and relevant information. At the end of
the day, that is what search engines are attempting to do: provide users with the
most relevant search results based on a searcher's query.
1 up, 0 down
Reply Permalink
Highbeam Research
September 10th, 2009 at 9:31 am
The way I understand it is every page, once metrics are assigned, has a % of its real
page rank that is can spend in whatever way it wants. So if a site wants to link out to
trusted sites in their industry and use this page rank in that way then it can. Or if they
choose to spend that juice internally to other relevant pages then they can do that as
well. There are benefits to both. The only thing I would be careful of is linking to
competitors with good anchor text as you don ’t want to help them gain relevancy for
competitive keywords.
1 up, 0 down
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jennita
September 10th, 2009 at 8:30 pm
As SEO's I believe we often overthink everything. If it makes sense to link to another
source (one that you trust isn't spam) then link to it.
1 up, 0 down
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rui.jiang
September 10th, 2009 at 7:10 am
wow, I just had a feeling that something big will come up today.
Great post, rand, it's really really comprehensive and pretty much covered
everything about link value
1 up, 0 down
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seo wizz
September 10th, 2009 at 7:16 am
Ever since Matt Cutts comment on 'editorial' type links I have been carrying out
various tests trying to establish the exact effect of naturally given links built
into content, for example a blog post.
The results so far have been very positive with some pages moving up 2 pages
on Google by simply applying some anchor targeted links in the content of a
blog post.
A fairly new link building tactic is offering sites unique content for an anchored
link back to your site, this might be a great idea if Google are going to give so
much weight to editorial links.
Great article, covers all the bases and a little more.
2 up, 0 down
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14. Great article, covers all the bases and a little more.
2 up, 0 down
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Dr. Pete
September 10th, 2009 at 7:46 am
I hate to leave a fan ­boy comment, but this is really a great resource. It's
clear, both from clients and the Q&A here on the site, that many people still
have a very narrow view of link ­building, usually focusing on quantity over
quality (or, at best, one very small aspect of quality). The algos are becoming
more complex every day, and a one ­trick­pony approach to SEO just doesn't
cut it anymore.
1 up, 0 down
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rorycarlyle
September 10th, 2009 at 7:55 am
My internet induced ADD didn't allow me to focus properly on this post ­ it's
long. I'll need a few rereads to make this all stick. I've got most of this down,
but 17 is an impressive amount of link factors.
Thanks, Rand.
1 up, 0 down
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James
Svoboda September 10th, 2009 at 8:07 am
Even though this list is extremely through, there seems to be no mention of the
RankRank ® metric that was at first a cornerstone of the Webfluence linking
formula and is rumored to have recently made it's way into the Googoritm; ­)
­­­­­­­­­­­­­­­­­­­­­­­
On a more serious note there are a few other coding issues and server
directives that can affect link juice or “link visibility”:
l robots.txt instructions
l .htaccess, 301, 302 & 404
l Meta Index & Follow tags
l Canonical tags and Duplicate content
l Framed & Iframe pages
l Links embedded in Flash and Silverlight
l Word, Excel and PDF docs that contain links
­­­­­­­­­­­­­­­­­­­­­­­
Also, really great post!
Edited by James Svoboda on September 10th, 2009 at 8:09 am
4 up, 0 down
Reply Permalink
garypool
September 10th, 2009 at 8:10 am
Thanks Rand,
More tools for my client explanation arsenal.
Keep 'em comming.
1 up, 0 down
Reply Permalink
vizioninteractive

15. Reply Permalink
vizioninteractive
September 10th, 2009 at 8:17 am
Great overview post, Rand. I believe you've touched on just about everything
there is to say about links. Personally, I am definitely seeing good results when
link building and targeting many different domains rather than links from the
same sites. Diversity is a good thing.
Not sure if you technically mentioned it above, but links in the middle of a
sentence seem to be given more weight...rather than some anchor text link in a
sidebar. Definitely worthy to note.
I also have seen evidence that links from pages that have a lot of traffic tend to
help, as well, even if they're nofollow links.
1 up, 0 down
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carfeu
September 10th, 2009 at 9:27 am
Great post. I would be curious to know if a link to a page was incorrect but still
worked (using for instance upper rather than lowercase) if the engines would
frown upon it somewhat?
Oh... and with HTML5 links in content will be valued far more, because by then
the spider can understand much better what the main content is and what is
not.
Edited by carfeu on September 10th, 2009 at 9:28 am
3 up, 0 down
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neopunisher
September 10th, 2009 at 9:35 am
totally awesome article and lots of useful information. thanks for the post
1 up, 0 down
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ASL Internet
September 10th, 2009 at 10:46 am
Another Great post, Very informative!
1 up, 0 down
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Michael
Martinez September 10th, 2009 at 10:48 am
"Search engines likely use scores about the "authority" of a domain in counting
links, and thus, despite the fuzzy language, it's worth mentioning as a data
point. "
On what do you base this conclusion? What publicly verifiable information are
you able to share about "domain authority", "domain pagerank", and other
domain­related concepts you advocate?
Your ranking factors survey is not an authoritative document in these matters.
What else do you have to share on the topic?
1 up, 0 down
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firegolem
September 10th, 2009 at 11:07 am

16. 1 up, 0 down
Reply Permalink
firegolem
September 10th, 2009 at 11:07 am
With what do you refute his claims?
A) you can ask Rand to further back up his claims
B) you could disprove his claims
In my opinion hes done a lot of good work here already. If you would like to contribute,
you could try to actively disprove his claims and everyone can learn something new.
4 up, 1 down
Reply Permalink
Michael Martinez
September 10th, 2009 at 11:22 am
"With what do you refute his claims?"
I'm not refuting anything. I'm asking for specific information.
1 up, 4 down
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firegolem
September 10th, 2009 at 2:57 pm
"Your ranking factors survey is not an authoritative document"
Reads like refuting to me...
3 up, 1 down
Reply Permalink
Michael Martinez
September 10th, 2009 at 3:22 pm
" 'Your ranking factors survey is not an authoritative document'
Reads like refuting to me..."
Not to me. I asked Rand for specific information, but wanted to make it
clear that an opinion poll is not an appropriate source of information.
1 up, 3 down
Reply Permalink
Nick Gerner
September 10th, 2009 at 2:11 pm
Michael,
Good question. Obviously search engineers aren't disclosing the specifics of the algorithm
(Sarah could chime in about legal issues around trade secrets). But I have two good
arguments that the notion of domain authority makes sense and we can use it in SEO:
1) Experience tells (many of) us that it works. Our industry survey is pretty broad and
there's high consensus that this is a factor that many SEOs are using. Our own
quantitative studies puts measures of domain authority way up there regardless of page­
specific factors.
2) The state of the art research (including from Yahoo! Research and Microsoft Research)
focuses on domain level metrics. The arguments cited in the papers come in two flavors.
First it's much easier to create measures of authority globally to domains and then apply
them to constituent pages (which are much more numerous and change more quickly
than global calculations can keep up with). And second, statistically speaking pages within
the same domain share many of the same properties (spamminess, quality, truthfulness,
value to searchers, etc.)

17. specific factors.
2) The state of the art research (including from Yahoo! Research and Microsoft Research)
focuses on domain level metrics. The arguments cited in the papers come in two flavors.
First it's much easier to create measures of authority globally to domains and then apply
them to constituent pages (which are much more numerous and change more quickly
than global calculations can keep up with). And second, statistically speaking pages within
the same domain share many of the same properties (spamminess, quality, truthfulness,
value to searchers, etc.)
Consider a selection of Web Spam research focusing on domain level factors:
l Fetterly, et al. Spam, Damn Spam, and Statistics
l Gyongyi, et al. Combating Web Spam with TrustRank
l Castillo, et al. A Reference Collection for Web Spam
l Abernethy, et al. Web Spam Identification Through Content and Hyperlinks
Whew! I have a bunch more citations if you like. Feel free to PM me :)
Edited by Nick Gerner on September 10th, 2009 at 2:14 pm
6 up, 0 down
Reply Permalink
Michael Martinez
September 10th, 2009 at 4:04 pm
Nick: " .... I have two good arguments that the notion of domain authority makes
sense and we can use it in SEO"
First of all, Nick, while I appreciate the response, making "use of it (domain
authority) in SEO" has nothing to do with the assertion that "search engines likely
use scores about the 'authority' of a domain in counting links, and thus, despite the
fuzzy language, it's worth mentioning as a data point."
What was once a supposition has almost become a statement of fact. If we're going
to talk about this concept as an established fact, I want to know who established the
fact, when, and where.
The papers you refer to are old hat ­­ everyone has read them. None of them have
anything to do with the question.
Your industry survey doesn't represent what the search engines are doing ­­ it
represents what people think is important to Google's ranking algorithm (and I
participated in the first version of that survey, so I'm quite familiar with how it
comes together).
" 2) The state of the art research (including from Yahoo! Research and Microsoft
Research) focuses on domain level metrics...."
Yes, and I can point you to patent application reviews on Bill Slawski's site that deal
with these topics.
None of that has anything to do with my question. We know that Yahoo! and
Microsoft have expressed an interest in domain ­level evaluations ­­ Yahoo! has
even publicly stated that the first link from a "site" counts more than the rest in
their algorithm (without explaining how they determine which is the first link).
Search engines have long had the means to identify reciprocal links between
"hosts", but the classic definition of a "host" is not limited or constricted to include
only domains.
The papers you listed don't even speak about domains (not in this context) ­­ they
are concerned with "hosts", which what the literature tends to focus on, as the
majority of sites are not equivalent to domains.
The SEO community has built up a huge myth around the idea of "domain
authority", leaching the name from the old Hilltop and LocalRank papers with no
real understanding of what those papers were addressing (Hilltop was developed for
Google News in 2002 but many people in the SEO community wrongly assert it was
rolled out in the 2003 October update despite numerous denials from Google
employees that they use the Hilltop logic in Main Web Search).
Last year John Conde cogently debunked a lot of this "domain authority" mythology
and no one has yet adequately responded to him.
We all recognize that some domains are more trusted than others ­­ but trust does
not equal the ubiquitous "authority" that the SEO community talks about without
really defining the concept clearly.
What's domain authority? Rand has never offered a technical definition ­­ he just
sprinkles the term liberally throughout his posts and presentations.
Someone recently asked me what the best way to determine how a page passes
link juice may be. I had to ask back, "What is link juice?" I'm familiar enough with
the term as Rand loves to use it, but no one has ever bothered to explain what it is.
Is Link Juice = PageRank? Is it Anchor Text? Is it Trust? Is it a combination of 2 or

18.
What's domain authority? Rand has never offered a technical definition ­­ he just
sprinkles the term liberally throughout his posts and presentations.
Someone recently asked me what the best way to determine how a page passes
link juice may be. I had to ask back, "What is link juice?" I'm familiar enough with
the term as Rand loves to use it, but no one has ever bothered to explain what it is.
Is Link Juice = PageRank? Is it Anchor Text? Is it Trust? Is it a combination of 2 or
3?
I don't want to PM you for citations ­­ I've probably read all the papers and patents
you can refer me to, and I'd even be willing to wager I've read some you haven't.
No one has offered a formal definition for "domain authority" and there has been
absolutely no indication from Google that they even use it.
What is it? Can you offer a concise definition that makes sense at all levels?
Last year I wrote:
... if we assume for the sake of discussion that Google does have some sort of
domain­level PageRank, they don ’t have to use it for weighting links or
adjusting relevance scores in search results. That is, a domain­level
PageRank ­like mechanism could be used to establish trust thresholds, to
identify neighborhoods, to create filtering processes that help Google figure
out where Web spam is, where new fountains of legitimate content have
sprung up, etc. That is, by mapping relationships between domains, Google
can analyze the Web without actually using that analysis to directly impact its
linking valuations or search results.
You guys have invested a lot of time, money, and resources into building a tool that
seeks to emulate a concept for which there is no established frame of reference.
We don't know if it exists within Google's algorithm.
We don't know how it would be used if it does exist within Google's algorithm.
We won't know how to measure it if it does exist within Google's algorithm.
What is the justification for all this talk about "domain authority" and "domain­level
PageRank"? Experience hasn't taught you or anyone else in the SEO community
(including me) anything about these concepts. None of us has any experience with
these concepts.
SEOmoz ­­ just like Yahoo! and Microsoft ­­ can do whatever it wants with its search
engine. So within LinkScape you have calculated these values but you haven't
shown that anyone else is using them.
Google really cannot use a "Domain authority" to weight its search rankings any
differently from the way PageRank weights search rankings. Google has made it
clear that "each site gets only so much PageRank" and that PageRank has to be
spread throughout the site as far as it can go to get as many pages to rank in
search results as possible.
If that's the purpose of PageRank, then what is the purpose of DomainRank? What
value does it provide in combatting Web spam? Yahoo.com is home to one of the
largest collections of Web spam ­­ and yet we all talk about Yahoo! as though it's a
highly trusted site.
Wikipedia is a terrible source of information ­­ its "facts" change constantly and its
authors/editors are so discredited that even one of Wikipedia's founders has tried to
come up with a better alternative (using vetted sources as contributors).
And yet we see Wikipedia all over the search results. Instead of crediting
Wikipedia's internal linking structure and extensive on ­page repetition of keywords
(as well as use of keywords in titles and URLs), many people in the SEO community
simply conclude that "Wikipedia is an authority domain " and that means it cannot be
beaten in the search results.
That's not acceptable. Where is the science behind these ideas? Where is the
publicly verifiable confirmation from ANY major search engine that this is a key
factor in its algorithm?
I'm all for canvassing the SEO community to see what people think is important ­­
but I draw the line at using opinion polls as authoritative documents about the inner
workings of search engine algorithms.
There is absolutely no credibility in that kind of position ­­ please don't retreat into
that document for lack of useful information.
Rand would do us all a favor to write a document explaining what he thinks "domain
authority" really is, how it works, and why it is needed by any search engine. So far
as I can determine, no one has really done that.
I'd like to know what everyone thinks they mean by "domain authority". I'm pretty
sure no two people can agree on what it should mean. Rand can help move the
conversation forward by putting forth a clear, concise explanation.
From there we can begin looking for empirical evidence (or just hound search
engine employees into talking about the validity of the concept).
Edited by Michael Martinez on September 10th, 2009 at 4:07 pm

19. I'd like to know what everyone thinks they mean by "domain authority". I'm pretty
sure no two people can agree on what it should mean. Rand can help move the
conversation forward by putting forth a clear, concise explanation.
From there we can begin looking for empirical evidence (or just hound search
engine employees into talking about the validity of the concept).
Edited by Michael Martinez on September 10th, 2009 at 4:07 pm
1 up, 2 down
Reply Permalink
Nick Gerner
September 10th, 2009 at 4:17 pm
You're clearly thinking a lot about this. I urge you to move this discussion to
a post of it's own. Maybe this is a great YouMoz post, or a discussion you can
continue in its own right.
I'd love to read more about your thoughts on the subject :)
7 up, 0 down
Reply Permalink
Michael Martinez
September 10th, 2009 at 5:46 pm
Nick: "You're clearly thinking a lot about this. I urge you to move this
discussion to a post of it's own. Maybe this is a great YouMoz post, or a
discussion you can continue in its own right."
Michael : I appreciate what you're saying, but what I'm asking for is a
very clear (and hopefully precise) explanation from Rand and the
SEOmoz team (or any other person to whom you guys would
specifically defer) what "domain authority" is supposed to mean.
I want to read YOUR thoughts (and Rand's) on this topic.
1 up, 0 down
Reply Permalink
jennita
September 10th, 2009 at 8:25 pm
"...explanation from Rand and the SEOmoz team..."
FYI... Nick *IS* on the SEOmoz team.
2 up, 0 down
Reply Permalink
firegolem
September 10th, 2009 at 5:32 pm
http://www.youtube.com/watch?v=qXgni6U6qk8&feature=related
Michael
Be interesting to get your take on Matt Cutts saying newsweek and time have
authority (in the context of domains) here.
3 up, 0 down
Reply Permalink
Michael Martinez
September 10th, 2009 at 5:49 pm
firegolem : "Be interesting to get your take on Matt Cutts saying

20. Reply Permalink
Michael Martinez
September 10th, 2009 at 5:49 pm
firegolem : "Be interesting to get your take on Matt Cutts saying
newsweek and time have authority (in the context of domains) here. "
Michael : I LONG for the day when Matt Cutts or any appropriate
Googler explains in meticulous detail what they mean by "trustworthy
and reputable sites" at the algorithmic level.
I'll make a deal with you. When that happens, if I see it first, I'll
contact you ­­ as long as you contact me if you see it first.
1 up, 0 down
Reply Permalink
goodnewscowboy
September 10th, 2009 at 6:17 pm
Funny. As I was reading through the post earlier today, I noticed how some things were
worded and I found myself wondering if you would weigh in in in your inimitable style
Michael.
You didn't disappoint :)
For starters, unless you are a fly on the wall at the Googleplex, you aren't going to get
your answers. I know that. I'm sure you know that. So why, oh why do you keep beating
the same drum?
Rand filled the post with dis­qualifiers such as "likely", "some feel", "potentially" and
"possibly".
What that means to me is: use this at your discretion, and test it out yourself.
I'm grateful that he brought these items out of the "speculative" closet so I can be aware
of them and it gives me a leg up in the SEO process.
Why not take what you want and leave what you don't want, instead of demanding more?
2 up, 1 down
Reply Permalink
BrettBorders
September 10th, 2009 at 1:17 pm
Great post, Rand! a solid summary of link value factors that I tend to agree
with, based on my own experience.
1 up, 0 down
Reply Permalink
sly­grrr
September 10th, 2009 at 1:59 pm
Rand, as always, great stuff.
I seriously doubt that without actually getting Search Engine Employees to give
actual proof of concept inside information there is going to be a better way to
explain this to a client.
What is astonishing (to me at least) is that this is only one area of the
determined merit of a website for search results purposes. Although extremely
important, it's only one part of the puzzle.
Thanks for the awesome work.
1 up, 0 down
Reply Permalink
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A Developer's Adventure Into the World of SEO
This Week in Search for 9/10/09

21. Add Comment
A Developer's Adventure Into the World of SEO
This Week in Search for 9/10/09
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