Google search engine as the free source of traffic has the right to banned your domain name or penalize your website URL if you go against search engine traffic like building unnatural links, buying backlinks, and using unethical means to gain backlinks like the use of black hat means. When your domain name is banned from search engine, you will found out that you no longer rank for your targeted keyword, no matter how you tried to. Banning a domain is just search engine blacklisting your domain URL and that connote it will be ignore by search engine crawler no matter how much you tried to rank for any keyword.
For everything Google search engine does, there is always a reason for that and perhaps for the reason why your Domain name was banned or penalized by search engine, you must have followed unethical means of ranking for the particular keywords you are so concern about.
Aside from this, Google can penalize domain name if such domain name is having too much of its links from domain name that has been penalized by search engine such as Google itself, Yahoo and Bing.
So, if you care to know whether Google has penalized your domain name, the following tools will help your out whether your URL has been banned or not. These are the tools you can use to check whether my domain name was penalized by search engine or not, but quite fortunate my domain name wasn’t penalized.