Since half an hour I get the message: http://arduino.esp8266.com/stable/package_esp8266com_index.json using Arduino IDE 1.6.8. with boardmanager 2.0.0. However when I try this link in a browser, I see an JSON file. This morning everything worked OK. I disabled my PC firewall and virusscanner, but the error stays. Could there be a syntax error in the http://arduino.esp8266.com/stable/package_esp8266com_index.json file?