Hi 
Since yesterday I am not able to download anything from downloads.arduino.cc - neither the IDE itself, nor the browser plugin, nor can I read the index from http://downloads.arduino.cc/packages/package_index.json when I open the board manager in the IDE.
Am I trying an obsolete approach to downloading stuff from Arduino or there is an actual issue? Are there any plans to when the site will be back up?
Can you load the URL in your browser:
http://downloads.arduino.cc/packages/package_index.json
works for me but I have had problems in the past where I could open the URL in my browser but the Arduino IDE could not. Usually this is related to your network security settings such as firewall but for me I didn't change anything, it stopped working, then a couple weeks later it started working again.
Turns out (after your input that the server is down only for me) that my provider is probably blacklisted or something and after playing with some proxies I managed to get it to work. Thanks