IE receiving HTTP 1.0 response for some files

Question

I've included an audio and video player (html5 with flash fallback) which works in all browsers except IE.

While looking for the problem I found that the server sends "HTTP/1.0 200 OK" and "Connection:close" headers (and no Content-Length), but only in IE and only for some files (including .swf, .mp3 and .mp4).

I have added the following to .htaccess to disable gzip for those files:

<IfModule mod_env.c>
  SetEnvIfNoCase Request_URI "\.(?:mp3|mp4)$" no-gzip dont-vary
</IfModule>

I have no experience with apache configurations and no idea why a different http version should be used for some requests.

Here are the send headers:

GET /test.mp3 HTTP/1.1
Accept  */*
User-Agent  Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Trident/5.0)
Accept-Encoding gzip, deflate
Host    ------
Connection  Keep-Alive

and the response headers:

HTTP/1.0 200 OK
Date    Wed, 13 Jun 2012 07:38:17 GMT
Server  Apache/2.2.22 (Unix) mod_fcgid/2.3.6 mod_ssl/2.2.22 OpenSSL/0.9.8g
Last-Modified   Mon, 04 Jun 2012 13:15:25 GMT
ETag    "1bc12b-596969-4c1a553b51540"
Accept-Ranges   bytes
Connection  close
Content-Type    audio/mpeg

UPDATE: I just found out that the initial page request (PHP, text/html) response is also HTTP/1.0 but not all subsequent ajax requests.

Answer 1

The problem was with an old configuration option in apache that was never removed from the default configuration:

http://blogs.msdn.com/b/ieinternals/archive/2011/03/26/https-and-connection-close-is-your-apache-modssl-server-configuration-set-to-slow.aspx