Preventing quit of Firefox I'm planning to show a presentation of my websites to friends on Firefox, but I do not want them to exit full screen and terminate the Firefox application, but only to click the elements on the screen, similar to the browsing of computers in a store?

How is this possible?
There are several Add Ons which provide Kiosk modes for Firefox. You should search Here.

For several card catalog search stations in my school's Library, I've been used the Kiosk Mode in the iCab browser for many years.

Kiosk mode - While in Kiosk mode, iCab will cover the whole screen and all other applications are blocked. The Kiosk mode is the ideal environment when the computer is accessing a public place (like fairs, exhibitions, hotels etc.) where users should be able to obtain information, yet prevent any external access to your system. Additionally, the access can be restricted to certain pages (even refusing referrals, if you choose).