Possibly the question should be why does GWT not support the current Release of Firefox. What is the GWT you refer to ? * Possibly http://www.gwtproject.org/overview.html You may also be interested in * ( AMO ) Add-on Developer Hub https://addons.mozilla.org/developers/ * ( MDN ) https://developer.mozilla.org/Add-ons ** [https://developer.mozilla.org/Add-ons/SDK /Add-ons/SDK] ** [https://developer.mozilla.org/docs/Games /docs/Game] **https://developer.mozilla.org/en-US/docs/Games/Introduction_to_HTML5_Game_Gevelopment_%28summary%29 {sic} Development with a G in the link ** [https://developer.mozilla.org/en-US/Apps/Tutorials/General/Foundations_of_an_HTML5_Web_App Tutorial]