After the dissolution of Yugoslavia (.yu) in the 1990s, the independent country of Serbia and Montenegro (Crna Gora i Srbija in Serbian) was assigned the ccTLD .cs (yes, the same one previously assigned to Czechoslovakia). During this time, the .cs extension was never assigned an operator and was not used. The Republic of Serbia then became an independent state in 2006, after Montenegro (now using .me) left the union. According to documents on the official website (http://www.rnids.rs/include/data/list0032_en.pdf), existing .yu domains can be converted to .rs domains before general registration is opened to the public.

Serbia: Start of .rs domain registration March 10.
Serbian National Register of Internet Domain Names (RNIDS) informs Serbian and international public that registration of the new Internet domain names of the Republic of Serbia with .rs extension, will commence on Monday, March 10, 2008 at 12h noon.

RNIDS will accept requests for registration of new .yu domain names until Friday, February 29, 2008. After this date registration of new .yu domain names will no longer be possible. All .yu domain names registered until this date will continue to function normally at least until September 30, 2009.

Registration of new .rs domains will be conducted through 27 Serbian companies, which were accredited by RNIDS as the accredited registrars of .rs domain names.

List of the accredited registrars of .rs domain names, as well as detailed rules and procedures regarding .rs registration and transition from .yu to .rs, are available at Web site www.rnids.rs.

(Source: Economy.co.yu, February 28. Link to article)