How can I disable spell checking in Firefox? This is not a trivial question. The normal option to turn it off does not work. Version is 29.1
Here is a screenshot showing the option turned off yet spell checking is still happening:
This is done by Google, not the browser.
As you can see in the image below, if you inspect the code, you can see it uses the class
If you remove this class (or overwrite it using GreaseMonkey or similar) the misspelt word is no longer underlined.