I would like to use the fact the browsers can be installed in various languages as a way to practice my French. So if I am in Firefox and see the word "options" in the menu and want to know how it is translated in the French version, I would like to click a button to switch the browser language to French quickly and then use the French version until I don't understand one of the French words, then switch back to English, etc.
Are there any browsers which allow me to switch languages dynamically in this way without reinstalling?
Addendum
The quick-locale-switcher that freethinker suggested seems to switch the language of the add-on but not the language of the browser, or am I missing something?
