Russia has made rhetorically linked NATO's actions in Kosovo to what it is currently doing in Georgia. Dunno how long they've been linking the two, but the Kosovo war was in 1999.
I don’t recall that they did link the Balkans and the Caucasus at that time but may not have noticed. Serbia is a traditional Russian ally. Stomping on the Serbs made Russia very hot about it (thank you President Clinton). Arguably NATO’s attack on Serbia is what brought Putin to power. Anyway, the domains were registered in June 1999, Putin became president on December 31, 1999 (per Wiki).
The whole “linkage” argument becomes more spurious by the day though. I don’t recall NATO forces marching on Belgrade.