TYPO3 Core

Included CSS and JS files is cached by the browser, but when one file is changed, the is often problems with the browsers ability to re-cache the changed file.
This leads into a backend that doesn't work correctly or have design flaws, which brings support questions from editors and so on.

Version number all these files in order to have a unique filename for every file. By using .htaccess rules, it is possible to create a virtual filename using the files modification time (filemtime). This way version numbering is fully automatic and the filename will change from filename.js to filename.1260819325.js.

Additional information is available in the TYPO3 core list where an RFC will be posted in a few minutes.
(issue imported from #M13998)