I guess you’ve already seen the warning message of Firefox when you try to modify it’s settings. The warnings tells you that you should not configure or edit any settings if you don’t understand any of it because it affect the performance, stability and security of Firefox. If you tweak your Firefox settings a lot then it will be more handy to disable temporarily, fortunately there is an easy way to disable it just uncheck the “Show this warning next time” checkbox and the message will be gone. But what if you want to bring it back? Here is the very easy steps to re-enable about:config warning message.
Type in about:config into the address bar, scroll down and look for the following:
Double click the item and change it’s value back to true and the warning message will appear again.