About cache

As per HTTP basic user-agent should not cache URL's with query string. In the latest firefox browser you can very easy check out the current cache. Just use the following URL: about:cache And what can I see for example

Key: http://www.reddit.com/button.js?t=2
Data size: 371 bytes
Fetch count: 1
Last modified: 2009-07-22 14:51:00
Expires: 1970-01-01 03:00:00

And by the way the picture will be the same not only for firefox. Always make unique URL's if cache is an issue for your application. E.g. link taglib lets you add an unique query string attribute in order to avoid client-side cache