Although Domain Authority is only an indicator of Moz.com to measure the popularity of your site and does not directly determine whether you will rank high for a certain keyword, it is nice to know how many links you need to increase your Domain Authority and it is a quick and easy indicator to determine the value of a site or page.
Domain Authority is a better indicator to determine if a site is worth getting a link from then Pagerank which was Google metric and has been discontinued. You can download the free SEOBook Toolbar to view this data from every page you visit.
Below we briefly explain Pagerank value which is similar to Domain Authority:
(Image source: Elliance)
Below an example calculation for the PageRank score:
PageRank 1 = 10 PageRank points
PageRank 2 = 100 PageRank points
PageRank 3 = 1000 PageRank points
PageRank 4 = 10000 PageRank points
PageRank 5 = 100000 PageRank points
How many PageRank points 1 link can pass to your site depends on the quality and quantity of this incoming link. It is important when passing on PageRank that it is a dofollow link.
The above illustration shows us that the Google Toolbar Pagerank says little, because a page with PR 4 can be a page with 10000 PR points, but it can also be one with 99999 PR points.
Google PageRank Updates, when will my site get a PR update?
The Google Toolbar Pagerank is not kept up to date in real time. On average, the Google Toolbar PR is updated once every six months. And since the Toolbar PR is not logarithmic, it can be concluded that the Google Toolbar Pagerank is not very accurate in determining link value.
Link Value Determining:
To determine the value of a link, we use other metrics such as the SEOmoz Domain authority, Page authority metrics and the Alexa Ranking. This information is important to determine whether it is worth the investment to purchase a link or determine the value of selling links from your own site. In addition to these values, it is important to know how well a page ranks on the keyword for which we want to rank well with link building. Of course the page is relevant which is another important indicator for determining the link value. The link value is divided by the number of links on the page, both internal and outgoing link. The TrustRank of a link and thus link value increases the longer the link is on a page. Content links have more value than, for example, footer or sidebar links. The link is then surrounded by relevant text.
Note: Frequent purchase of links from sites that advertise purchasing links from their site may incur a penalty. So we will never do. Buying links is possible when this is not openly advertised as Google cannot find out. In addition, purchasing links from pages with authority (for example important directories such as BOTW and Homepage.nl (often also free)) has a favorable effect on your ranking and Trustrank and will therefore not result in a penalty.