http://blog.csdn.net/violet_day/article/details/18734421
https://developer.mozilla.org/en-US/docs/Mozilla/Preferences/Mozilla_networking_preferences#Cache
在地址栏输入：about:config
然后在过滤器中输入：browser.cache.disk.enable
解释：When a page is loaded, it can be cached so it doesn’t need to be downloaded to be redisplayed. For e-mail and news, messages and attachments are cached as well. This preference controls whether to use the hard drive for caching purposes. browser.cache.disk.capacity controls the maximum amount of disk space to use.
设置为false
done
补充：
网上还有一篇文章介绍如何关闭缓存
在地址栏输入：about:config
在过滤器中输入：network.http.use-cache
解释：When a page is loaded, it can be cached so it doesn’t need to be downloaded to be redisplayed. This preference controls whether to cache files retrieved by HTTP or HTTPS either in memory or on disk.
设置为：false
done
总结：貌似两者都有用。
还有一个属性：browser.cache.memory.enable
network.http.use-cache 指设置不缓存。
browser.cache.disk.enable/browser.cache.memory.enable 指上面的属性打开（true）后，设置保存在disk还是memory。
所以，network.http.use-cache是前提。