Page Authority?Page Authority predicts the likelihood of a single page to rank well, regardless of its content. The higher the Page Authority, the greater the potential for that individual page to rank well in search results.
How is Page Authority Scored?
We score Page Authority on a 100-point, logarithmic scale. Thus, it's easier to grow your score from 20 to 30 than it would be to grow from 70 to 80. We constantly update the algorithm used to calculate Page Authority, so you may see your score fluctuate from time to time.
Page Authority vs. Domain Authority
Whereas Page Authority measures the predictive ranking strength of a single page, Domain Authority measures the strength of entire domains or subdomains. The same is true for metrics such as MozRank and MozTrust.
Where can you find Page Authority?
Page Authority metrics are incorporated into dozens of SEO and online marketing platforms across the web.
You can measure Domain Authority using Open Site Explorer or the MozBar, SEOWAPS free SEO toolbar.
Technical Definition of Page Authority
Page Authority is SEOmoz's calculated metric for how well a given webpage is likely to rank in Google.com's search results. It is based off of the Linkscape web index and includes link counts, mozRank, mozTrust, and dozens more. It uses a machine learning model to predicatively find an algorithm that best correlates with rankings across thousands of search results that we predict against.
It's best to use Page Authority (PA) and Domain Authority (DA) as comparative metrics when doing research in the search results and determining which sites/pages may have more powerful/important link profiles than another. While more specific metrics like mozRank can answer questions of raw link popularity and link counts can show the raw quantities of pages/sites linking, the authority numbers are high level metrics that attempt to answer the question "How strong are this page's/site's links in terms of helping them rank for queries in Google.com?"
SEO Best Practice
How do I influence this metric?
Unlike other SEO metrics, Page Authority is difficult to directly influence. This is because it is made up of an aggregate of metrics (mozRank, mozTrust, link profile, etc...) that each have an impact on this score. This was done intentionally because this metric is meant to approximate how competitive a given site is in Google.com. Since, Google.com takes into account a lot of factors, a metric that tries to calculate it must incorporate a lot of factors as well.
This means the best way to influence this metric is to improve your overall SEO. Particularly you should focus on your link profile (which influences mozRank and mozTrust) by getting more links from other well linked to pages.