Question : GZip Partially Working

I've set up IIS6 to use GZip. Its a local test server using Win Serv 2003

All the settings are correct as far as I can see:

gzip-pics.png (55 KB) (File Type Details)

Settings from IIS Meta Explorer

and I get the following response header for the asp page:

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Cache-Control: private
Date: Mon, 28 Jun 2010 10:54:15 GMT
Content-Type: text/html
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
Content-Encoding: gzip
Vary: Accept-Encoding
Transfer-Encoding: chunked

200 OK

However, according to YSlow the CSS file is not being compressed. If I just run the CCS file on its own I get the following response header which show its not being zipped:

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Cache-Control: max-age=31536000
Content-Length: 14883
Content-Type: text/css
Last-Modified: Fri, 25 Jun 2010 15:57:39 GMT
Accept-Ranges: bytes
Server: Microsoft-IIS/6.0
X-Powered-By: ASP.NET
Date: Mon, 28 Jun 2010 10:53:39 GMT
Vary: Accept-Encoding

200 OK

I have Helicon Tech's ISAPI Rewrite running on the server too. But that was an issue, it wouldn't compress the asp page either (??). The CSS file appears in the gzip temp file which is really confusing.

So am I relying too much on what YSlow is saying and all is OK or is there something amiss?

Any help would be greatly appreciated.

Regs,
Numb

PS I've just run a test html file and that doesn't have gzip listed in the response header either but YSlow gives it the all clear???

Answer : GZip Partially Working

I Think I've found the answer to my own question!

It turned out to be some rules set in our Isapi rewrite config file. Once I commented them out it all sprang into life!

Just for the record here are the culprits (I've not ested to find exactly which one yet):

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# 480 weeks
#<FilesMatch "\.(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$">
#Header set Cache-Control "max-age=290304000, public"
#</FilesMatch>
 
# 2 DAYS
#<FilesMatch "\.(xml|txt)$">
#Header set Cache-Control "max-age=172800, public, must-revalidate"
#</FilesMatch>
 
# 2 HOURS
#<FilesMatch "\.(html|htm)$">
#Header set Cache-Control "max-age=7200, must-revalidate"
#</FilesMatch>

#<FilesMatch "\.(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$">
#Header set Expires "Mon, 31 Dec 2012 20:00:00 GMT"
#</FilesMatch>

#RewriteCond  %{HTTP_USER_AGENT}  MSIE.[56]     [I]
#RewriteCond  %{HTTP_USER_AGENT}  (?!SV1)       [I]        
#RewriteHeader Accept-Encoding: .* none