Domain registration operator .CO Internet announced today that the company has registered the one millionth .CO domain name, less than a year after launching in July 2010.

.CO Internet thanks Overstock, Amazon and Twitter (among others) for the rapid growth. Overstock internationally rebranded its operation O.CO and the domain name has been featured across Web and Internet advertising, giving the .CO domain great visibility. The millionth .CO domain was registered at GoDaddy, which .CO Internet says is the largest retailer of .CO domain names globally.

"Mainstream awareness of .co is building with huge brands like Amazon, Twitter, and Overstock; and so is awareness of entrepreneurs that their next domain doesn't need to be 23 letters long or lack vowels or cost a million dollars," said Naval Ravikant, founder of Angel List (Angel.CO), in a press release.

The .CO domain designation is the country-code top-level domain (ccTLD) for the country of Colombia, which has blessed the use of .CO in "a responsible and secure manner" according to the .CO Internet frequently asked questions. As a top-level domain, .CO is treated the same way in search results as a .com domain.

.CO is not bound to Internet Corporation for Assigned Names and Numbers (ICANN) policies because of its designation as a ccTLD. That does not mean that .CO Internet has not set up ICANN best practices, it just operates outside of the jurisdiction of ICANN framework.

To protect the rights of trademark owners, .CO has partnered with network connectivity company Neustar and consultant firm Deloitte for validation. Hence, if you own a trademarked Web property, .CO will be able to work with you to keep your .CO URL, should a company want to squat on their own domain name or set up a different vertical within the business (or rebrand the company, as Overstock did).