Here’s how to disable FireFox’s browser cache completely.

1. Fire up FireFox
2. Type about:config in your address bar
3. Type ‘cache’ in the search bar, and look for network.http.use-cache, and double click it to set it to false. Double clicking it again will set it to true and re-enable the cache

…and then you’re done.

To forcibly reload a page and all its dependencies, direct from source, ignoring local and proxy caches hold the shift key and hit reload. This applies not only to FireFox but also IE6/7 and Safari (maybe others too). I have a feeling this may be a ratified standard.

This has also been suggested

I set browser.cache.disk.enable and browser.cache.memory.enable both to false.

That was all I had to do to disable caching.