"Content is king"—which means it is mandatory to have unique, informative, and interesting content, in short—quality content on our website. However, content alone is insufficient to appear on the first pages of search engines.

Without a link-building promotion campaign, the content will be a lone king on a planet (your website) that no one knows about and can't see even with the most powerful periscope—an exotic planet, lost somewhere in the infinite universe (internet). So, you need link-building for other mortals to learn about the wonders that populate your site.

But link-building can be as powerful as it is dangerous if you "friend" the wrong people. Just like in real life, in link-building, you need to know who you accept in your circle of friends, collaborators, or business partners. Below is a list of five of the most important criteria that will help you avoid sites you shouldn't have backlinks from.

1. Irrelevant Sites

The number of backlinks matters—the more you have, the better. Ideally, the number of domains from which you obtain backlinks should be as high as possible, but some specialists confirm that, in the future, there is nothing wrong with having several links from the same site; on the contrary, it helps.

However, make sure that the sites you want to get backlinks from are relevant to your site—that is, they are from the same niche or related niches. An exception would be generalist sites, such as news sites, but ideally, the site you're going to get that backlink from should have something in common with your site's niche.

There is room for creativity, even more than you think, and you can opt for many combinations as long as they make common sense; however, be careful not to get a link from an agricultural blog for your audio equipment and installation site.

2. Sites with Poor-Quality Content

Website content must be of good quality, not just relevant. But what is good-quality content? Here are some key features:

• The site has many articles.
• The site is updated frequently.
• The articles are rich with useful information.
• The articles are up-to-date.
• The articles are unique and not copied from elsewhere.

3. Sites with Little or No Authority

A site's low authority can hide serious problems. If a site is new or young, it is natural to have low authority; a link on such a site can be a good long-term investment, as long as the website is relevant to our site and will not be compromised in the future by spammy SEO techniques.

If that site is years old and still hasn't managed to build authority in all that time, then it's best to avoid it and move on.

After the disappearance of the PR authority indicator (PageRank) offered by Google, it was necessary to choose alternative solutions for evaluating websites. Currently, the SEO community mainly uses platforms like Majestic SEO and Ahrefs; these are premium services that can provide very useful information about a domain's authority. I use the free TF (Trust Flow) and CF (Citation Flow) indicators provided by Majestic SEO when evaluating the authority of a domain/site.

4. Sites That Have Poor-Quality Backlinks

This is a more delicate situation that requires a lot of attention—these are sites that have high authority because they have a large number of backlinks, but they are toxic "friends." The problem is that these sites often have low-quality, spammy backlinks that give them false authority.

I recommend a thorough analysis using one of the services mentioned above (Majestic or Ahrefs), especially if we will be doing link-building for a client. A free but brief assessment—however, by no means sufficient or definitive—is the analysis of TF and CF indicators and the relationship between them.

In short:

• Install the Majestic Backlink Analyzer Chrome extension
• Extract the values of the two indicators, TF and CF.
• Interpret them: ideally, the CF value should be lower than TF or not much higher (TF/CF > 0.75). This means that a relatively small number of sites have provided high authority to the domain. Otherwise, if we see a very high value for CF and a small number for TF, it means that authority (TF value) was obtained through a very large number of poor-quality backlinks.

To the previously mentioned indicators, I would also add the MOZ Spam Score, offered by MOZ within the Open Site Explorer service. Although not as accurate as TF and CF, this Spam Score is another factor I take into account when I want to avoid a spammy site. Ideally, a site that is clean and reliable will have a Spam Score of 0 or 1 at most.

5. Sites That Link to Low-Quality Sites (Directories))

In this case, we are talking about sites that have authority and a clean backlinks profile (no spammy backlinks). We need to see which sites they are sending links to (outbound links). This can be done very easily with Screaming Frog's apps (partly free) or Xenu’s Link Sleuth (fully free).

This category mainly includes directories—sites created specifically for link-building. There are exceptions, such as niche directories relevant to your business, but most directories are spammy and created solely for SEO. I recommend a very careful analysis of directories or opting for other, less risky link sources.

Bonus Criterion: Sites That Are Part of PBNs

Some people own blog networks (Private Blog Network or PBN) where they post links to other sites for a fee. Leaving aside the fact that purchasing links is prohibited by Google, the mere presence of a backlink in such a network can attract a penalty.

Here's some pretty bad news—a PBN can be hard or impossible to spot if done by an experienced person. However, building such a network has become more and more complicated, and most are far from perfect. Here are some obvious signs of a PBN network:

• The sites within the network have an almost identical design.
• The sites within the network have very similar content.
• The sites within the network have similar IPs; usually, the Class C in IPs is identical.

Now that you have an idea of where you shouldn't put links to your site, you can choose one of two paths:

• If you are passionate about SEO, I recommend deepening your knowledge of the points listed above and adding other criteria discovered by you.
• If you were planning to do link-building for your business website, maybe it would be a better idea to turn to an experienced SEO specialist.

Whatever your decision, at this point, you know the most important disciplines that the sites linking to your website must score 10 on.

An article by Marius Bujor.