[users@httpd] "Last-Modified" response header is not returned for particular file names

[Siarhei Khirevich <kh...@googlemail.com>]

Hi,

I change hosting of my website, and currently try Ubuntu + LAMP as new web
site platform. (Apache version is 2.2.22) For some webpages I use
xmlhttprequest in javascript function to get modification time of other
pages using "Last-Modified" response header, but I found that for
particular file names (at least containing ".html" and ".htm") after making
"HEAD" (or "GET") request the "Last-Modified" header is missing among other
headers. If I rename target file, say, from "a.html" to "a" or "a.ht",
"Last-Modified" presents and I finally get modification time of that file.
It seems that "Last-Modified" response header is suppressed somewhere by
Apache (probably due to optimization reasons), and the question is how to
setup Apache to provide "Last-Modified" for any file name. Just note that
the problem is observed with empty httpd.conf, as well as use
of headers_module did not resolve the issue.

Regards,
Siarhei