Domain Authority (DA)
The domain authority of a website describes its relevance for a specific subject area or industry. This relevance has a direct impact on its ranking by search engines.

Domain authority can be described through four dimensions:

prestige of a website and its authors

quality of the information presented

information and website centrality

competitive situation around a subject

Page Authority (PA)

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.

Page Authority gets a score between 1 and 100 that tells readers how “authoritative” a page is in presentation.

Domain Authority measures the predictive ranking strength of entire domains or subdomains, Page Authority measures the strength of individual page. The same is true for metrics such as MozRank and MozTrust.


Prestige of website and authors
Prestige identifies the prominent actors in a qualitative and quantitative manner on the basis of Graph theory. A website is considered a node. The prestige of a website is defined by the quantity of nodes that have directed edges pointing on the website and the quality of those nodes. The nodes’ quality is also defined through their prestige. This definition assures that a prestigious website is not only pointed at by many other websites but that those pointing websites are prestigious themselves.

Similar to the prestige of a website, the contributing authors’ prestige is taken into consideration, in those cases, where the authors are named and identified (e.g., with their Twitter or Google Plus profile]. In this case, prestige is measured with the prestige of the authors who quote them or refer to them and the quantity of referrals which these authors receive. Search engines use additional factors to scrutinize the websites’ prestige. To do so, Google’s PageRank looks at factors like link-diversification and link-dynamics: When too many links are coming from the same domain or webmaster, there is a risk of Black Hat SEO. When backlinks grow rapidly, this nourishes suspicion of Spam or Black Hat SEO as origin. In addition Google looks at factors like the public availability of the WhoIs information of the domain owner, the use of global Top-level domains, domain age and volatility of ownership to assess their apparent prestige. Lastly search engines look at the traffic and the amount of organic searches for a site as the amount of traffic should be congruent to the level of prestige that a website has in a certain domain.

Information quality
Information quality describes the value which information provides to the reader. Wang and Strong categorize assessable dimensions of information into …

intrinsic (accuracy, objectivity, believability, reputation),

contextual (relevancy, value-added/authenticity, timelessness, completeness, quantity),

representational (interpretability, format, coherence, compatibility) and accessible (accessibility and access security).

Humans can base their judgments on quality based on experience in judging content, style and grammatical correctness. Information systems like search engines need indirect means, allowing concluding on the quality of information. Google’s PageRank algorithm takes approximately 200 ranking factors included in a learning algorithm to assess information quality.

Information and website centrality
Prominent actors have extensive and living relationships with other (prominent) actors. This makes them more visible and the content more relevant, interlinked and useful. Centrality from a graph-theoretical perspective describes unidirectional relationships, not making a distinction between receiving and sending information. From this point of view, it includes the inbound links considered in the definition of “prestige” complemented with outgoing links. Another difference between prestige and centrality is that the measure of prestige counts for a complete website or an author, whereas centrality can be considered on a more granular level like one individual blog post. Search engines look at various factors to judge the quality of outgoing links, i.e., on link-centrality, describing the quality and quantity as well as the relevance of outgoing links and the prestige of its destination. They also look at the frequency of new content publication (“freshness of information”) to be sure that the website is still an active player in the community.

Competitive situation around a subject
The domain authority that a website attains is not the only factor which defines its positioning in the SERPs of search engines. The second important factor is the competitiveness of a specific sector. Subjects like SEO are very competitive. A website needs to outperform the prestige of competing websites to attain domain authority. This prestige, relative to other websites, can be defined as “relative domain authority.”