If you have not already added the “noscript” toolbar button on the toolbar then add it by clicking on the menu button, then click on “Customize…”.
This will show the list of toolbar buttons as illustrated. Simply drag-n-drop the “noscript” button to the toolbar. Click the “Done” button at the bottom of the page when done.
The difference between the two is one button is only temporarily applying the change and the other one keeps the change.