Presently the address redirects to Rockstar Games' GTA V feed, but was originally a fansite. Also the recently registered HungoverX by Take-Two isn't GTA related, but XCOM.
Given the name registered it seemed that HungoverX was another viral website campaign set to launch in the run up to Grand Theft Auto V's release, but it's aliens instead!
HungoverX is actually attached to the impending launch of The Bureau: XCOM Declassified, and is anthat's available to be 'played' right now. The Bureau: XCOM Declassified releases on PC, Xbox 360 and PS3 August 20th in the US, 23rd in EU. Grand Theft Auto V releases on Xbox 360 and PS3 September 17th.