One of the biggest and most enduring search ranking factors is the link. Links have been important since the very dawn of search engines, and I can guarantee they will be important for as long as search engines exist. Links are the foundation of SEO, but they’ve changed a lot over the years.
In the very early dates, a link was a vote. That was pretty much all there was to it. A site with more links was a site with more votes, and it appeared higher in the search results. Obviously, this was very easy to abuse, and abused it was.
Since then, there has been an ongoing arms race between marketers on the dark side of the rules and the search engines themselves. One of the latest weapons in that race was Google’s Penguin algorithm, which helps assign values to links and penalizes sites that abuse them in a negative way.
The thing is, you don’t need to know any of this to learn how to analyze links. All you need to know is what makes a good link and what a bad link looks like.
There’s a lot that goes into the analysis of a given link. Every link that exists has to meet these criteria to be considered a good link. Good links are valuable; bad links are not. The worst links can actually be negative in value, which can hurt your site just to have them.
The link has to be followed. The link attribute “nofollow” prevents the search engines from actually “clicking” the link, which means that it might as well not exist. This is the attribute you use for user-submitted links like in comments sections, or links to sites you don’t support or condone, like spam sites you’re using as an example. This is just a simple technical restriction, and it’s a tool you can use to help shape Google results. It’s also why so many people are always on the hunt for followed links in guest posting opportunities and the like.
Now, a nofollowed link with your site name as anchor text can still be valuable to your site. It’s functionally the same as plain text without a link, and counts as an implied link or unlinked mention. Some people like to use brand mentions as link opportunities, but they also work just fine to build your brand and to provide some minor search value as they are.
The link has to be from a relevant source. If your site is about gardening, a link from another gardening site is a pretty good link. A link from a high quality gardening site is great. A link from a site about DIY home improvement is relevant enough and can still be valuable, but isn’t quite as valuable as the other links. A link from a game site reviewing Plants Vs. Zombies isn’t going to be a very valuable link at all. A link from a casino site might be a very poor link and would probably be considered spam.
The reasoning behind this is that Google wants more than just blind votes, they want votes from people who know what they’re talking about. You wouldn’t want an auto mechanic performing brain surgery on you, you wouldn’t want a programmer working on your car, and you won’t need to care about the opinions of someone completely outside of their field.
The link has to be from a trustworthy source. Anybody can throw a blog out into the wild at the drop of a hat. I can have one up on WordPress.com with a handful of basic blog posts in the span of a couple hours, and that’s if I have to write the content myself. That doesn’t mean my site is any good, though, so what use are its links? If your site is about gardening and I make and throw up a gardening blog and link it to you, that link isn’t going to be worth much.
There are a few things that make up the trustworthiness of a site. One of them is age; the older a site is, the more trust it has built up over time. This is, however, jeopardized if that site has taken negative or black hat actions in the past. Think of trust as a rating you build up over time, and lose when you break the rules. You have to take the time to build it up again in a show of good faith, and if you betray that trust too many times you can suffer permanently for it.
There’s also a flow of trust from one trusted source to another. If a highly trusted source links to a site that then links to you, that link has a certain amount of trust flowing from point A to point B to point C. Authority by association. It’s the basis behind Majestic’s TrustFlow metric, if you want a direct way to analyze it.
Trust begins in a set of seed sites. Wikipedia is a trusted site, as is the BBC, the Huffington Post, and dozens of others. The seeds of trust radiate outwards, diminishing with each degree of separation. Sites with no trust flowing into them have a hard time getting their links to matter, which is part of why negative SEO is so false.
The link has to be functional as a link and send traffic. After all, the original and primary purpose of a link is to ferry traffic from one page to another, right? If the link doesn’t actually send any traffic, as measured in Google Analytics, the link loses some value. This is a very minor factor, though, because traffic can be spoofed, the site might not use Analytics, and other flaws exist as well.
As an addendum to that, the link has to be positioned in a beneficial place. A link prominently displayed in the content of a post is going to be more valuable than a link in a sidebar, which is going to be more valuable than a link in the footer, which is more valuable than a link that’s usually hidden behind scripts. Links that are stashed in a way that makes them hidden, like behind images or hidden over a background of the same color as the text are actually detrimental, but not to you if you’re being linked; it’s a punishment reserved for the site making the bad decision to try to spam links.
The link should have relevant anchor text. Now, there’s a lot of variation and flexibility in anchor text. The value of a link goes up if the anchor text is a variation or a match to the keywords you’re targeting with your article. However, if you have too many links with identical anchor text, particularly if they’re all built around the same time, you end up with anchor text optimization problems and can actually hurt yourself. This is because one of the ways people would abuse links in the past was to build sites and link to themselves through private blog networks, and those links tended to be identical.
The link should come from a varied source. A link from Moz is a good link for any marketer, right? Well, sure, but if you have 5 links from Moz and 0 links from any other websites, you don’t have a varied link profile. You have a profile that looks like one guy on Moz is trying to market you and failing. The more variation you have from your backlinks, the better those backlinks are. Essentially, links from the same source to the same content have diminishing returns.
The link should be one-way. This is a bit of protection against reciprocal link schemes and link exchanges, which had sites A and B make a deal to link to each other.
A 1:1 link back and forth, particularly when it’s articles linking to each other, can be detrimental in large numbers. That’s not to say you should avoid linking to a site when it has linked to you, of course; just avoid repaying every link you get with a link of your own.
So, now you know what goes into a good link. There are a few other factors, but they’re relatively minor, even compared to the minor factors on the list. As long as your links meet most or all of the above conditions, they’re going to be good, beneficial links. So what do bad links look like?
Links from link exchanges are bad. Even if it’s a link wheel where site A links to site B links to site C links to site A, it’s pretty easy for Google to detect and monitor. A few individual 1:1 reciprocal links are fine, but when you get into very common link exchanges, it can be detrimental all around. Worse, if one site loses trust, it can bring the whole network down.
Links from blog networks. A blog network is a bunch of interlinked sites – or not linked sites, all run by the same person – that all link to one money site at roughly the same time. They used to be pure spam sites that got automated link updates, and they have grown more sophisticated in the years since, but the concept is still the same; artificially forcing link value on a money site to circumvent the organic growth process.
The problem with private blog networks is that they work, for a while. It takes time for Google to identify the sites in a private blog network, verify that it is indeed a private blog network, and take appropriate action to penalize it for being a private blog network. That means people always argue that they work, even when over time they stop working and can have a hugely detrimental effect on your site when they crash and burn.
Links from widgets and other embeds. The common practice for using a site badge or some other passive “powered by” widget is to nofollow the links in it. Links coming from a widget that aren’t nofollowed but are for some reason enforced or encouraged can be detrimental. GoDaddy is one of the prime offenders for this type of penalty, but many have been affected by it before.
Links from advertorials, press releases, and other forms of duplicated content. Links that come from such content tend to have a payment associated with them, either you paying them or them paying you. Google doesn’t want money in SEO, so they penalize advertorial links. At least nofollow them; that keeps the link juice from flowing but maintains their purpose as traffic generators.
Links that are present site-wide. Remember how I said a footer link isn’t all that valuable? That’s because it’s a site-wide link. Every time your site creates a new page, there’s that link in the footer. These links also suffer from diminishing returns, so any site being linked this way is only getting the value of a couple of links while the rest are mostly valueless.
Links from foreign webpages. One of the common forms of link spam is to buy a few thousand links from foreign pages. If your English site has a ton of links coming in from Russian sites, those links are pretty well guaranteed to not be valuable. There are a few rare exceptions, but for the most part any foreign link is going to be valueless to you.
Links from sites with penalties. If a site has a lot of spun content, a lot of stolen content, or issues with link penalties of their own, that site has lost a lot of trust and is likely suffering under a Google penalty of some sort. If that site has no value in itself, it has no value to pass to you, so you can get nothing out of it.
You get the idea. There are dozens of examples I could continue to list, but they all violate one of the first section rules in some way or another. Anything that costs a site trust costs the link its value. Anything that can deindex a site removes the value of that link. It’s all simple, once you have the list in front of you.
Can’t believe I’m the first commenter on here–it’s a great post. Regarding link wheels, I would say this–they still work great when it comes to reputation management. If you just want to earn a bunch of SERP results for a person’s name, for instance (like “attorney john doe”), then you can use well-made (that is the key) and regularly-updated sites to feature that person’s name rather than linking constantly. This keeps you away from black-hat link penalties while allowing you to crowd out negative 1st page results for your client’s name over time.