the domain is fooked for some reasons. Steve says it will probably be back tonight, so try again tomorrow :P
But the servers are still up. And to access the hotline server use hl.cortana.org instead of hl.forerunners.org. I also suggest people that have not checked out forerunners to check out our hotline server at hl.cortana.org or hl.forerunners.org (f.org is not working right now tho), there you can find LOTZ of marathon fans, bungie fans, wideload fans, halo fans, myth fans, gnop fans... and so on. :)
So.. everybody, you're welcome :)
note: those who don't know what hotline is, then it's an irc like program, frogblast (search versiontracker) is a good client for osx.