Domain authority is a classification on a domain named based around many factors. The domain authority of a website will depend on how old it is, how long it has been on Google, how many backlinks it has and how many backlinks it has from other authority domains. The higher domain authority on a website the better chance it has of ranking well in Google.
We use a tool which is free for everyone to use called Open Site Explorer to track domain authority. Domain authority is similar to Google Page Rank, where a website is ranked in authority by the amount of other websites linking to it. Google Page Rank has become increasingly difficult to track because manipulation has forced Google to keep these figures secret, and they only release them every 12 months or so. With Open Site Explorer we can get a better judge of domain authority. The higher the domain authority the better a website will perform on Google. We should see this rise in accordance with a link building campaign.