when super cache does not set last modified times and etags?
i have seen once that it does not set them and even also expires header!
sometimes i have seen that it set them all.
it was hard to me to check it that time , because i did not know how to use firefox with other profile and have not installed any other browser. by the way, a blog post about how to use several profiles, even in same time: http://lifehacker.com/software/firefox/geek-to-live--manage-multiple-firefox-profiles-231646.php .
i should to check it without cookies of blog or with clear profile because if they exist super-cache can start wp-cache (which is other).
but even if it was wp-cache, i think it would be good if it could return only header with 304 "not modified" status without sending content at all.
i think super-cache must do that, because/when it returns simple files for which apache(,for example, and probably many others) calculate etag itself and uses file's last-modified time.
and is there difference of super cache(+wp-cache) behavior when setting expires, etag, last-modified http headers among different types of pages: pages like "about", month archive pages, post pages, category pages?