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What’s in a link? Simple answer: ‘link juice’. Of course if you’re not familiar with the term that won’t really mean much, but the basic idea is that some of the strength of the page containing the link (or ‘juice’) is passed through to the linked site. But how much juice is passed? How valuable is a link from site A compared to site B?

The precise workings of Google’s ranking and link grading algorithms isn’t known except by the smartest and most secretive of bods at Google HQ, however people make a damn good effort to backward engineer and predict the algorithm workings to replicate the rankings and search results given by Google.

SEOmoz

roger-seomozAt Attacat part of our SEO toolkit is SEOmoz, who have created a range of metrics for grading websites and web pages for their ‘juice’ or value. The scales are usually logarithmic, so it’s harder to bump up a grade higher up the scale. MozTrust is a 1–10 grade of distance from ‘trustworthy’ web sources, often things like Government, University or BBC-type sites. MozRank is a link popularity score, grading from 1–10 based upon the number of links into a site or page.

The SEOmoz rankings of primary interest, however, are Page Authority and Domain Authority. These are basically the overall figure of how valuable and likely a page or domain respectively is to rank well, and therefore how much value a link passes comparatively. These scores are based on a 100 point logarithmic scale, and are their closest correlation to Google’s search rankings.

A newly created page will have relatively low page authority but will benefit from the higher domain authority of the entire domain, so may still be ranked fairly well while it builds up its own page authority. Attacat.co.uk, for example, currently has a domain authority of 35, however the homepage has a page authority 0f 42. So the homepage is seen to be more important and have more value than the domain as a whole (homepages are often the most valued and authoritative).

Page authority is a’ changin’

new and old page authority

SEOmoz yesterday revealed that their metrics and the complex algorithms behind them have changed. This is especially important news if you use SEOmoz, as you may notice a change in your authority scores in the next few weeks.

No, this won’t be (entirely) down to the wonderful linkbuilding and SEO work being done on your site, so it’s important to take a note of the ranking changes if you use domain or page authority as a performance metric in any way.

You can find a stats-heavy and technical explanation of the changes on the SEOmoz blog – interesting but hardcore!

Even with changed figures comparative analysis between domains and pages will still work and be very valuable, but be careful about viewing your particular domain’s figures in a bubble.

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