I just downloaded the Android ADT package (eclipse + Android SDK) from here , and I tried to install new software from
Help → Install new software ...
but an error always occurs (exception). The repository I'm trying to download is http://dl-ssl.google.com/android/eclipse-preview/ and the error

I am not behind a proxy server, and I do not understand what the problem is. I also tried to execute the various answers found here on stackoverflow, but the problem is still with me! Thanks for helping me.