Unlike many other addons that at first glance appears to do the same thing,
THIS one does it RIGHT.
When JS is turned off this way it trigger the standard noscript-tag, which developers use to tell visitors if they need JS to use functions on a site.
Unless this is done properly, you may never know that for example the form you just submitted was just thrown away instead of submitted.
It also has some nice preferences you can set, AND a clearly visible on/off-state.
THIS is how you do it.