Recently, I wanted to disable JavaScript on a website in Firefox, because it was disabling mouse right-click context-menu and I could not view the source code of the webpage. To my intense surprise, I found out that the feature to disable JavaScript has been removed from Firefox 23 and above. This is very much undesirable. After some research I found out an add-on called SettingSanity that can add this feature back in Firefox. The SettingSanity extension adds the options to disable images, tab bar and JavaScript back in the Firefox Options window.
You can install the SettingSanity extension from the Mozilla add-ons website. The installation of this add-on requires you to restart the web browser and it can be used immediately after the restart. After the restart, you will see no change in the main Firefox window. But if you open the Options window for Firefox (through Tools → Options menubar or from Firefox → Options → Options), you would see new options listed under the Content section.
The newly added options (Load images automatically and Enable JavaScript) work just like they worked in the older versions of Firefox. The Load Images automatically option can be used to disable the loading of the images on a webpage. The Enable JavaScript option allows you to block JavaScript in Firefox for all the websites.
Under the General section in the Firefox options, it also adds the options to disable tab bar when only one tab is being used. The option Always show the tab bar can be used to toggle the tab bar when there is no real need of it.
So if you are feeling disoriented after an hour of looking for the JavaScript disabling options in the new versions of Firefox, then relax and just install the SettingSanity extension in Firefox. In a matter of seconds, you would have these options back in Firefox and then you can once again disable JavaScript in your favorite web browser.
You can download and install the SettingSanity add-on from https://addons.mozilla.org/.