Yes, I know.. . . .WTF is Firefox doing here, it's a browser not a resolver. If anyone from Firefox reads this, WHY ?? Let people who want this useless function enable it themselves and not the other way around.
Now to disable it, very simple is the procedure, and very very intuitive.. .aheum:
- Open a new tab and go to about:config
- Search for network.dnsCacheExpiration
- If you don't have it, add it (right click "new Integer")
- Set value to 0
Oh, and don't mess it up because if you create the wrong key or make a boolean rather than a string you can't delete the key or modify its properties, only the value.