Following this question, what does A and A* mean for conference rank? Is there a site where can I get information for conference rank?
In computer science, the most important ranking is the one maintained by CORE, the Computing Research and Education Association of Australasia. It uses ranks such as A* (=exceptional), A (=excellent), B (=good to very good), and C (=sound and satisfactory).
They make the criteria for the different ranks explicit in a formal ranking description document.
Also, they have an online database with their rankings.