Far too many of us in the SEO industry tend to think in absolute terms. You are either White Hat or Black Hat, this works or it doesn't, this link is amazing or it is worthless...you get the point.

This is dangerous thinking because if something isn't absolutely perfect or golden, we tend to evaluate it as useless. In nothing is this more obvious than in link building.

Link builders come from two schools of thinking. They either (a), pursue and take any link from anywhere or (b), research and scrutinize every potential link opportunity.

If you think like the first group, then this post is not for you. But if you are in the second group, this post should help you evaluate the value of a link.

The anatomy of a link can be thought of in five parts: anchor text, trust, relevance, placement and outbound links. Each one makes up a piece of the link pie.

I already know what you are thinking- what about authority? The five pieces of the pie mentioned above are what make the pie, but authority is what determines the size of the pie.

This means that if your link is on a high quality, authoritative website, search engines will pay a lot more attention to the metrics of that link that one on some spammy website.

Let's look at each individual metric then and see what they all mean.

1. Authority

As I just mentioned, authority is what determines the size of the pie. The more authority a domain has, the more weight search engines give to the metrics of their outbound links.

Tip: Any search in Google will bring up websites with domain authority at least in the thirties. If the website you are considering for a link opportunity does not have at least a 30 for domain authority, you won't get much value from it.

2. Anchor Text

For the better part of the last decade or so anchor text has been the most important metric of a link. Marketers understood this and it is precisely because of this metric we saw the rise of the Google Bomb.

Blog comment spam is another malady that is directly tied to the importance of anchor text. It's only because of this metric that I have to delete comments on my blog from readers like "cheap online cash advance overnight."

Exact match anchor text isn't the only way to be successful here. A website that sells mountain bikes and targets that keyword should not turn down a link with the anchor text "bicycles."

Tip: Try and get links with your keywords in the anchor text. Be sure to maintain some variety though; search engines can detect unnatural amounts of identical anchor text.

3. Trust

A lot of people struggle to understand the difference between authority and trust. SEOmoz has their own metrics called authority, mozRank and mozTrust. I would recommend reading up on them to get a better idea for the difference.

Building trust with search engines is key to achieving great rankings. There is only one way to build that trust and that is to get links from websites that have a lot of trust built up already.

Tip: Writing a press release is a great way to get some trustworthy links. Lots of news and media outlets have trust with the search engines.

4. Relevance

Relevance is a measure of how connected your content is to the page that is linking to you. It makes a lot more sense for an exercise blog to link to a website that sells treadmills and not one that sells telescopes.

It is difficult to determine how relevant another website is to you however. One handy way is to use the LDA tool from SEOmoz. Just plug in your keyword and the URL of the page you are looking at and see how relevant it is to that term.

Tip: Try to get links from websites that have similar content to yours.

5. Placement

The original PageRank formula by Google treated all links on a web page the same. Each one would pass an equal amount of PageRank. This was called the Random Surfer Model.

Google and other search engines are a bit more advanced now. Bill Slawski explains how Google could be using a Reasonable Surfer Model in their current algorithm.

This means that having your link in the footer of a web page isn't going to help you out a whole lot. A contextual link right at the top of the page in the middle of the content is more likely to be clicked, and thus, likely to pass more PageRank.

The same is true of lists. People are a lot more likely to click links at the top of the list, so those links could pass more link juice.

Tip: Get links that have a higher chance of actually being clicked.

6. Outbound Links

If all links on a page passed an equal amount of PageRank, then more outbound links on a page meant less PageRank per link. Every outbound link on a page devalues your link ever so slightly.

This is why some directories seem pretty useless these days. With hundreds of links on a page, what value is there in adding just one more?

Tip: Don't post links on link farms or other pages with lots and lots of links already on them.

Conclusion

Back to my original point: in the SEO industry we tend to think all or nothing. It's not uncommon to see people turn down a link opportunity with great anchor text and great placement on a relevant page because it didn't have much trust or authority.

This seems flawed to me. Just because you can't get every piece of the pie you don't want any of it? Why turn down a little just because you can't have a lot?

The same goes for partial pieces. A partial anchor text match is not as good as an exact anchor text match, but it's better than nothing.

I'm not saying you have to settle for any link from anywhere, but if you can get even two pieces of the pie, I would take it, even if you don't get the other three.