INTERNET SEES THE EXTINCTION OF FOUR LETTER DOTCOM DOMAINS
Every possible combination of four-letter domain names has been registered as of December 2013. The 4,56,976 combinations that can be made ranging from AAAA to ZZZZ have all been used up. The three-character domains have been used up since 1997.
Courtesy: The Times of India, Chennai, Oct 16, 2014