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.

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