The extension is very useful. where sites require javascript it can be switched on. Where java scripts cause problems, freezes etc, it can be switched off. I had a problem with the JS Switcher symbol not being visible in my browser address bar. I emailed the developer who responded alsmost instantly - he is very helpful indeed. Eventually I found two reasons why I couldn't see the icon. Firstly, it only appears on http/s web pages and not on the firefox new tab, add-ons, or options pages, for example. Secondly, in customising the toolbars, I had a "flexible space" to each side of the address bar, which reduced the size of the address bar and appeared to cut off the JS icon. Easy to fix by removing the flexible space via customise. With these issues sorted, and in light of the very helpful developer, I am happy to give 5*.