Link Popularity - A Definition.
Link popularity, also known as link pop, link juice and link reputation is the generic term we give an algorithmic component used by search engines to analyze the quantity and quality of links pointing to a web page. Ask.com, Google, Live Search (MSN) and Yahoo! use some form of it and it's considered a major factor in their ranking algorithms.
Link popularity is generally considered a numeric factor, but the overall concept incorporates three additional factors - quality, relevance and anchor text. Their importance varies by engine but it's widely accepted that large numbers of topically relevant, trusted inbound links using keyword anchors will influence ranking. Here's a breakdown of each of the link pop factors:
Quantity denotes the number of inbound links to a webpage. At one time this was the main criteria of link popularity but now we know it's not just about numbers.
The second component is relevancy. Securing links from simi liar or on-topic sites is desirable and shows a relationship between two sites via the content in and around the links.
Quality is a measurement of authority assigned to a webpage by the number and type of inbound links it receives. Authority pages tend to rank well and have large numbers of inbound links from other authority and hub sites. Links from these pages carry higher endorsements as the link popularity is trusted and channeled to the host site.
Last but not least is anchor text. This is the clickable part of the link you see which plays the important role of telling both human and search engine what's coming up on the page being linked to. Anchor influence supports keyword phrases both as an inbound link and on site content.
While the search engines don't share the exact components of link popularity or indicate which factors are weighted more heavily, they have provided us with limited insights into parts of their algorithms. The most famous of these is PageRank.
PageRank, is exclusive to Google and considered the heart of their algorithm. PageRank is a link analysis algorithm that assigns a numerical weighting to each element of a hyperlinked set of documents. We know it's influence has been tweaked and changed over the years based on how pages are currently ranked and from comments made by various Google representatives. Google allows us to see a general representation of PageRank scores through their toolbar but also points out it's not a true picture of all the quality factors associated with a page.
As for the other three engines, Ask says it uses ExpertRank in their algos and since Yahoo now owns the patent for TrustRank it's probably safe to assume they're using it to some extent. After looking around and not finding anything on what MSN is using I pinged the great patent guru and my friend Bill Slawski of SEOByTheSea fame and asked for help. In typical Bill fashion I got back a mini-novel of information and my answer: The algorithm that Microsoft has written the most about is their RankNet approach. Writing about and using are two different things of course but hey, I wanted something here from MSN!
Bottom line, all four of these engines/algorirthms use link popularity as part of their ranking process. They might call it by another name or emphasize different aspects but it's being used in each algo.Until another ranking factor comes to light, it's a good idea to have a basic knowledge of what link popularity is and how to use it to complement your marketing tactics.
Why You Need Link Popularity To Succeed.
If you're link building to support ongoing SEO efforts, you want to secure links with keyword anchors from topically relevant, aged authoritative websites. These convey the greatest amount of link popularity which in turn will help your site to rank well. Or simply, you need a lot of links using keyword anchors from well ranked websites in and around your industry that have been online awhile. Doing so not only helps your site rank for a given set of keywords, but also drives targeted visitors to your site.
That said, a link is a link is still a link no matter where it resides until you determine a goal for it. If its SEO support, avoid links from pages that aren't in the main search index, have no unique inbounds or use some sort of tracking code and/or exclusion tags. On the flip side, these aren't issues if you're building awareness or linking for traffic. In that case all you need is to get links on pages your buying public frequents.
Not All Link Popularity Flows Freely
Back in the old days (1999-2003 ish), it was accepted opinion that PageRank leaked through outbound links. As a result webmasters were reluctant to link out for fear of losing their measure of green. Thankfully that issue has been quieted in part to comments like these but a new one about PageRank hoarding via the nofollow attribute seems to be making the rounds. The job description for that little attribute just keeps growing every day!
So what is nofollow anyway? The nofollow attribute is called "nofollow" with rel="nofollow" being the format inserted within an anchor tag. When added to any link, it will serve as a flag that the link has not been explicitly approved by the site owner. The terms "link condom" and pink links are associated with the use of the nofollow attribute, both flag the link as being "nofollowed".
The attribute was created as a way for blog and guest book owners to control link spam. Its effectiveness as a spam deterrent is widely debated and we now have people using it to hoard PageRank from their own webpages. I think that's silly since you're basically annoucing you distrust your own material but - it's hard to change a PageRank tsunami once its started. (Look how long the PageRank Leaks conspiracy was out there!)
So what's this nofollow attribute look like? Here's an example of a regular link:
<a href ="http://www.myshoesite.com/page.html">Buy Shoes</a>
And an example with nofollow added:
<a href ="http://www.myshoesite.com/page.html" rel="nofollow">Buy Shoes</a>
When a search engine sees a link using the nofollow attribute (as in Example 2) it understands the site owner is not vouching for the link and doesn't impart any link popularity to it as a result. From there, each engine handles things a little differently.
In Google's case, they ignore the link and move on. Yahoo! spiders the link but doesn't allow it to pass any link reputation to the target site which is why links using nofollow will show up in Yahoo Site Explorer.
I can't find documentation on what MSN is doing on a per-link basis but did find where they restrict all robots from following links on a page when CONTENT="nofollow" is used. (They also don't have a direct link to this info in their Help Central area so I can't cite it).
To be clear - just because a link uses nofollow doesn't preclude them from working. You can still click and move along but the link won't be indexed (Google) or pass link reputation (Yahoo!).
Ok, let's do a quick review and wrap up:
- Link popularity has four components - quantity, quality, relevance and anchor text. All important but weighted differently, only the engines know what's in the secret sauce.
- If you're linking to support SEO, secure relevant on-topic links from quality (authority) sites using keywords in the anchors.
- Nofollow attributes work differently with each engine; they allow people to pass but not link popularity. If you're linking for rank, avoid these links unless you find a way to turn the nofollow lemon into lemonade.
Further reading and tools:
How Google, Yahoo & Ask.com Treat the No Follow Link Attribute from Search Engine Journal
Link Popularity Check Tool from Marketleap
The Link Popularity Factors by Pandia SE News
The Search Status Tool that turns nofollowed links pink
Based in Williamsburg Virginia, Debra Mastaler is President of Alliance-Link, an interactive marketing company focused on providing custom link building campaigns and link training and is the author of the link building blog Link Spiel
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