Re: graphics cached by browser

At 10:39 -0800 2003-12-15, Susan L. Hedgpeth wrote:
>We just changed some graphics on our homepage. Some people's
>browsers are displaying combinations of the old and the new (which
>looks very bad). ... What do we do to make sure users are seeing the
>most updated graphics?

At 11:32 -0800 2003-12-15, Milan Andric wrote:
>I think that's [reload page in browser, perhaps also delete the
>local browser cache] about all you can do. Not sure if you already
>did, but try a different browser like mozilla to compare, and
>isolate the issue. Are you using a proxy by chance? I'm thinking
>something else might be caching it along the way, besides the
>browser.

At 12:00 -0800 2003-12-15, Graham A. Patterson wrote:
>The only way to avoid mixed graphics because of local browser caching is
>to ensure that the name of the graphic file is changed when the content
>of it changes. ... Then the browser treats the files as new,
>irrespective of local caching.

   Good suggestions. To add to this discussion, one article
summarizing these issues is:

   http://www.netmechanic.com/news/vol4/design_no5.htm

  The above article links to a second, highly detailed article on
caching of web content, and how to control it:

   http://wdvl.com/Internet/Cache/index.html

   This article suggests that setting a <meta http-equiv="expires"
...> tag on the relevant Web pages may help keep most Web browsers
from caching data on those pages -- so this technique will help
somewhat -- but won't work with most proxy servers.

   Setting the "Expires:" HTTP header at the server apparently should
work with both browsers and proxies, however. And a new category of
Cache-Control headers in HTTP 1.1 allows finer control of what can be
cached and what should not be.

   Graham's suggestion seems by far the most straightforward for
Susan's situation. However, if anyone might need to delve further
into browser and proxy caching behavior, the above articles might
serve as a good starting point. The latter includes some good
references and tools, at
<http://wdvl.com/Internet/Cache/ref.html#REF>.

Aron Roberts
Workstation Software Support Group
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Received on Mon Dec 15 12:24:48 2003