[thelist] Test before using "Cache-control: no-cache" HTTP header

Ben Gustafson ben_gustafson at lionbridge.com
Mon Dec 10 09:42:21 CST 2001


As a result of the recent discussion on thelist last week regarding web caching and proxy
servers, I added the header "Cache-control: no-cache, must-revalidate" to my employer's
corporate Web site. Later I tried downloading with IE one of the several PDF documents
that are on the site, and I was surprised to get the "What do you want to do with this
file" dialog. Choosing either "Save it to disk" or "Open it" both caused the following
dialog to appear:

	Internet Explorer cannot download doc.pdf from www.lionbridge.com.
	IE was not able to open this Internet site. The requested site is 
	either unavailable or can't be found.

I tried changing the HTTP header to "Cache-control: no-cache, must-revalidate", and
"Cache-control: no-cache". Neither fixed the problem. When I changed it to "Cache-control:
must-revalidate", however, the problem downloading PDFs went away. The Microsoft site says
that documents in formats such as PDF, .doc, .xls, etc., are not viewable in the browser
window in IE if you include cache-contol directives in the header. My experience seems to
point to the no-cache directive as the cause, but in general it looks like testing in
different browsers and different files types should be done when setting Cache-control
headers. More info on this issue can be found at the link below.

	http://support.microsoft.com/default.aspx?scid=kb;EN-US;q297822

--Ben Gustafson
  Lionbridge Technologies
  www.lionbridge.com




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