One note thought:

Atually as Steve pointed out in his comment to High Performance Web Sites: Rule 3 - Add an Expires Header the HTTP 1.1 specs says that URLs with query strings should not be cached only when there is no explicit expiration information:

From HTTP 1.1 spec, section 13.9:

e note one exception to this rule: since some applications have
traditionally used GETs and HEADs with query URLs (those containing a
“?” in the rel_path part) to perform operations with significant side
effects, caches MUST NOT treat responses to such URIs as fresh unless
the server provides an explicit expiration time.

Also, RoR have some kind of template tag for auto versioning and it uses QS as far as I know.

- Lukasz

Thanks very much for saving me several hours!

- rich

RewriteRule ^/static/([a-z-]+)\.[0-9]+\.(css|js) /static/$1\.$2 [L]

Is better.

It seems Opera and Safari don’t cache file paths with query strings, as per the HTTP spec, and given that it’s part of the spec we have no guarantee that other browsers won’t behave the same in the future. Probably best to do something like:

return path_string.replace('.css', '.%d.css' % mtime)

And have something like this in mod_rewrite:

RewriteRule ^/static/([a-z-]+)\.[0-9]+\.(css|js) /static/$1\.$s [L]

This keeps the filenames looking like: /static/css/style.1207433992.css, but rewrites them to the latest versions in your static server.