The answer to question 01: Generic TLDs are those maintained by ICANN (.com, .org, .net, .info, .biz), while the other main sets of TLDs are country codes and sponsored. The answer to question 02: Up to 63 alphanumeric characters and the hyphen. The answer to question 03: In windows: %SystemRoot%\system32\drivers\etc\ The answer to question 04: After the # character is treated as a comment.