ACRank: ACRank, or A Citation Rank, is a simple web-ranking metric created and tracked by Majestic SEO, a company that crawls links.
ACRank values are on a scale from 0-15 and are determined based on how many different root domains (or short domains) point back to a webpage. 0 is the lowest ranking, meaning it's the least significant to searchers and has the fewest links, and 15 is the highest, meaning it has a large number of unique domains referring users to the website.
The rank value compiles the number of short domains that link back to a webpage to determine its authority and relevance to online searchers. Short domains would be wordpress.com, while long domains would be along the lines of pictures.wordpress.com. A long domain with a www. address would just drop the www. to become a short domain.
The ACRank value doesn't account for the ACRank of pages that link to your page, meaning that building links from reputable and respected sources may not be as crucial as building links from a variety of sources. The weight of backlinks is not taken into account.
Essentially, Majestic SEO created ACRank to measure the value of websites for internet marketers and SEO specialists. Majestic SEO's website allows you to view how many ACRanked sites refer to your website.