user38069: I tried to download the ATmega16 board in my Arduino. I have set below URL under File->Preference->Additional board manager URL
https://mcudude.github.io/MightyCore/package_MCUdude_MightyCore_index.json
I am getting below attach images. How can we resolve this error and install atmega16 board manager? 
I am using Arduino version 1.6.9. I don't have any issue in opening MightyCare and Arudino URL from my chrome browser.


user38069: Thanks for everyone help here.
I have resolved by few steps.
1) File -> preference -> Board manager URL as like below. Basically URL are seperated by commas.
http://arduino.esp8266.com/stable/package_esp8266com_index.json,https://mcudude.github.io/MightyCore/package_MCUdude_MightyCore_index.json
2) Deleted the tmp file (package_index.json.tmp) which is in the path C:\Users\SIMBU\AppData\Local\Arduino15\ 
This helped me to resolve the issue.

38069: <p>I tried to download the ATmega16 board in my Arduino. I have set below URL under File->Preference->Additional board manager URL</p>

<p><code>https://mcudude.github.io/MightyCore/package_MCUdude_MightyCore_index.json</code></p>

<p>I am getting below attach images. How can we resolve this error and install atmega16 board manager? </p>

<p>I am using Arduino version 1.6.9. I don't have any issue in opening MightyCare and Arudino URL from my chrome browser.</p>

<p><a href="https://i.stack.imgur.com/0w920.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/0w920.jpg" alt="Error_in_BoardManager"></a></p>
 38069: <p>Thanks for everyone help here.</p>

<p>I have resolved by few steps.</p>

<p>1) File -> preference -> Board manager URL as like below. Basically URL are seperated by commas.
<code>http://arduino.esp8266.com/stable/package_esp8266com_index.json,https://mcudude.github.io/MightyCore/package_MCUdude_MightyCore_index.json</code></p>

<p>2) Deleted the tmp file (package_index.json.tmp) which is in the path <code>C:\Users\SIMBU\AppData\Local\Arduino15\</code> </p>

<p>This helped me to resolve the issue.</p>
