Right Encoding is added menu that set the character set on the context menu (mouse right-click) on Firefox and Thunderbird.
Right Encoding is developed by Go-Myung Kim (HeyGom or Gom - original developer), and he sent mail to me that he gives up management of this extension. And he left this module to the decision of me.
The ID of this extension conflict the id of original developer's extension because original developer registed AMO on past. So I'm must changing extension id. If you installed origianl developer's version (or right encoding 2 on AMO), after remove previous version and install this extension.
Firefox 29.0 and later, Thunderbird 1.0 and later