This post is a follow on my domain level metrics post , however you may also want to read Understanding Domain Trust and Authority before reading this post further.

In the last post I explained how PageRank is now also calculated on your domain, giving your domain an overall Rank that helps you rank newer pages faster on Google.

Today I wanted to touch specifically on authority or trust and there is a slight problem with what I am going to talk about, that is, it has not been confirmed by any of the major search engines.

However, most of the leading SEO authorities believe Google and co work out the trust level of a site using the following mechanism;

The theory was first put out their by Yahoo and was named “trust rank” it worked on the idea that all major search engines start their crawl of the web on a trusted domain, such as dmoz or the yahoo directory. Now depending on how far away your site is from these domains, in terms of links, it will determine how much your domain is trusted.

This theory is based on the common presumption that spammers link to spammers.

The following diagram shows how this may look:-

The further away you get from that trusted domain the less trust your domain will have. How does Google work out the trust of the Yahoo Directory?? The honest answer is who knows, age, outbound links. Probably a combination of hundreds of factors.

It has also been suggested that there is a mechanism called ‘reverse trust’ which looks at how far away your outbound links are from a spam site. This is why we always need to careful about who we link out to. The person we link to may not be a spam site but some of the people they link to may well be. Don’t be overly worried, remember the search engines have never confirmed this.

Domain Juice

This is a very simple concept and again it works in exactly the same way as PageRank.

The links back to your page give it a “Rank”, they also allow your pages to pass on link juice to another page.

Well… it works exactly the same with domains. Each link pointing to your domain gives the whole domain a rank, as per the previous post, however it also allows your domain to pass on “domain juice” to other domains.

So in the below diagram:

The numbers represent the amount of juice each page can pass, all these numbers are put together which gives a total amount of domain juice that can pass.

PR Zero Links

This is one of the reasons you should not worry about getting links from ‘pages’ with zero PageRank. Think about the domain as a whole. How much authority does it carry?

A good example is article marketing – If you write an article publish it on ezinearticles it will no doubt be on a page with zero PageRank, however what domain trust, authority, rank and juice does the ezine articles domain possess???

SEOmoz are the leaders in SEO tools in my opinion and their tool bar allows you to see domain level metrics.

In terms of ezine articles here is how their domain stacks up;

So is a link from a domain this strong worthless??? I don’t think so.

Understanding trust and rank on a domain level can help you better plan your link building strategy and assist you in getting higher rankings faster.

As always feel free to add to this or ask any questions.

I have always tried to explain seo concepts in a simple way, however there are some parts of SEO that still remain rather complex. This is more to do with Google’s lack of transparency rather than it just being down right difficult.

To be competent at SEO you first need to understand the link graph and how it gives search engines like Google, the power to turn the web into a hierarchical list based on relevance to a search query. Basically Google uses the link graph to understand the relevance, popularity and trust of your website to any given word search.

Initially Google only ranked pages, therefore each page of your website would be attributed PageRank based on the number and quality of links pointing to it, this is also known as Page Level Rank.

Every link back to your PAGE gives that page a rank based on the trust, relevance and authority of the links coming in.

Now Google has evolved it analyses those same metrics based on a domain level. Therefore Google will look at the overall links back to a domain as well as to each individual page. So if you have 1000 links pointing to multiple pages of your site they will all be counted as pointing to your domain and an appropriate domain rank will be established.

Below is a screen shot of the SEOmoz toolbar showing a domain rank and domain trust figure. Very helpful for deciding where to get your links from.

So Page Level Rank is assessed based on the number of pages linking in, this includes internal pages.

Domain Level Rank is assessed based on the number of links pointing at a domain from external sources.

Ok I hope you follow so far.

Why is this important??

Have you ever wondered why sites can rank a brand new page for a competitive keywords? Why when the BBC writes a new story it instantly hits the front pages of Google?

It is all based on Domain level metrics and Domain Rank is one of those metrics. The better your domain rank the stronger position you are going to be in to rank new pages within your directory.

Also knowing how domain level rank works should help you to better plan a link building strategy. For example a link from a deep page with 0 PageRank may be worth chasing if the domain has a good domain rank. I would much prefer a link from a deep page of the BBC with 0 PageRank than a home page of a PR3 that has little or no online presence.

There are other domain level metrics such as Domain Trust and Domain Juice and I will talk about them in my next post.

One last thing before I leave this post. If you have been link building on a new site and pointing all the links at the home page, there is a fundamental problem with this. As Google crawls the web and comes across your site it will notice in seconds that the majority of your links go to the homepage, so then why should Google not assume that the rest of the pages on your site are of no importance to it’s index? Afterall no one has bothered to link there.

An authorative domain will acquire links to many pages not just one, of course your home page is going to get the most attention but deeper pages should also earn their fair share of links.

If you have any questions or any points to add please do so in the comments.