This is difference between the default preference of Firefox

Diff between firefox 42.0 beta 1 default preference and firefox 41.0
　　　http://cat-in-136.github.io/2015/09/diff-between-firefox-420-beta-1-default.html
Diff between firefox 41.0 beta 3 default preference and firefox 40.0.2
　　　http://cat-in-136.github.io/2015/08/diff-between-firefox-410-beta-3-default.html
Diff between firefox 40.0 beta 3 default preference and firefox 39.0
　　　http://cat-in-136.github.io/2015/07/diff-between-firefox-400-beta-3-default.html
Diff between firefox 39.0 beta 3 default preference and firefox 38.0.5
　　　http://cat-in-136.github.io/2015/06/diff-between-firefox-390-beta-3-default.html
Diff between firefox 38.0 beta 1 default preference and firefox 37.0.1
　　　http://cat-in-136.github.io/2015/04/diff-between-firefox-380-beta-1-default.html