Mozilla Firefox about:config Tweaks

Accessing your about:config page
In your Firefox, type about:config in the address bar.

Disable Delay Time When Installing Add-on 

Config name: security.dialog_enable_delay
Default: 2000 (in msec)
Modified value:

• 0 – start installation immediately 
  
• any other value (in msec) 

View Source in Your Favorite Editor 
There are two configuration need to be made:
Config name: view_source.editor.external
Default: False
Modified value: True ( enable view source using external text editor)

Config name: view_source.editor.path
Default: blank
Modified value: insert the file path to your editor here.

Autohide Toolbar in Fullscreen mode  
Config name: browser.fullscreen.autohide
Default: True (always autohide)
Modified value: False (always show the toolbar)