How to turn off the Firefox cache?

Turn off the caching for a particular page. the correct way is to set the cache directive in Http request:

Cache-Control: no-cache

turn the entire Firefox caching capability off through its about:config page

network.http.use-cache = false.

If you use FireBug, on the Network tab's drop down menu there is an option do disable the browser's cache.

You can force all requests relating to a refresh to actually be requested from the server (bypassing any already cached content, and updating the cache with the new version) by using Ctrl+F5 instead of just F5.

This does not work for requests made by the page within client-side code though. When that is a problem you need to use the POST method (POST requests should never be cached) instead of GET or add an ever-changing value to the query string (such as the current time in ms).