The nameservers for quakelive.com changed and depending on your ISP it will take some time (a day) before all caches are updated.

To work around it, edit your %windir%\system32\drivers\etc\hosts file as Administrator and add this line:
50.23.229.123 www.quakelive.com

Now you can open http://www.quakelive.com website again and also connect to the game.