$cache_modified_check
If set to true, Smarty will respect the If-Modified-Since
header sent from the client. If the cached file timestamp has
not changed since the last visit, then a "304 Not Modified"
header will be sent instead of the content. This works only on
cached content without
{insert}
tags.
See also
$caching,
$cache_lifetime,
$cache_handler_func,
and
Caching section.