[squid-users] Squid return compressed page even when the request does not contains Accept-Encoding header

I'm using Squid version 2.6 stable 12.

When initially requesting the page http://ads1.msn.com/library/dap.js
with Accept-Encoding: gzip, I get the response properly. At the second
time, when requesting the same object with no Accept-Encoding header
at the request, I get again, the compressed response internally from
the cache. My browser is unable to parse this response.

Can anyone advise?

GET /library/dap.js HTTP/1.1
Host: ads1.msn.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; he; rv:1.9)
Gecko/2008052906 Firefox/3.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: he,en-US;q=0.7,en;q=0.3
Accept-Encoding: gzip
Accept-Charset: windows-1255,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive

HTTP/1.0 200 OK
Cache-Control: max-age=172800
Date: Mon, 23 Jun 2008 15:39:27 GMT
Content-Type: application/x-javascript
Last-Modified: Thu, 19 Jun 2008 20:59:23 GMT
Accept-Ranges: bytes
Server: Microsoft-IIS/6.0
pics-label: (PICS-1.1 "http://www.rsac.org/ratingsv01.html" l comment
"RSACi North America Server" by "inet_at_microsoft.com" r (n 0 s 0 v 0 l
0))
X-Powered-By: ASP.NET
P3P: CP="BUS CUR CONo FIN IVDo ONL OUR PHY SAMo TELo"
Content-Encoding: gzip
Expires: Mon, 23 Jun 2008 21:03:54 GMT
Content-Length: 4548
X-WR-MODIFICATION: Content-Length
X-Cache: MISS from NG_Cache
Via: 1.0 NG_Cache:3128 (squid/2.6.STABLE12-20070429)
Connection: keep-alive

GET /library/dap.js HTTP/1.1
Host: ads1.msn.com
User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; he; rv:1.9)
Gecko/2008052906 Firefox/3.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: he,en-US;q=0.7,en;q=0.3
Accept-Charset: windows-1255,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive

HTTP/1.0 200 OK
Cache-Control: max-age=172800
Date: Mon, 23 Jun 2008 15:39:27 GMT
Content-Type: application/x-javascript
Last-Modified: Thu, 19 Jun 2008 20:59:23 GMT
Accept-Ranges: bytes
Server: Microsoft-IIS/6.0
pics-label: (PICS-1.1 "http://www.rsac.org/ratingsv01.html" l comment
"RSACi North America Server" by "inet_at_microsoft.com" r (n 0 s 0 v 0 l
0))
X-Powered-By: ASP.NET
P3P: CP="BUS CUR CONo FIN IVDo ONL OUR PHY SAMo TELo"
Content-Encoding: gzip
Expires: Mon, 23 Jun 2008 21:03:54 GMT
Content-Length: 4548
X-WR-MODIFICATION: Content-Length
Age: 16
X-Cache: HIT from NG_Cache
Via: 1.0 NG_Cache:3128 (squid/2.6.STABLE12-20070429)
Connection: keep-alive
Received on Tue Jun 24 2008 - 06:25:23 MDT