WebKit makes no use of the If-Modified-Since HTTP header,
which makes static content service inefficient.
Of course, you can move your static content to a separate
HTTP server, but adding support for If-Modified-Since
buys most of the benefits and costs little.
The attached patch modifies mod_webkit to pass
the If-Modified-Since header via the request environment
dictionary. While arguably less than elegant,
this does the trick.
The patch to UnknownFileTypeServlet checks the
IMS value against the file's mtime. If it matches,
it sets "Status 304" and sends no content.
(It also corrects some unlikely but possible bugs.)