By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
435,446 Members | 3,031 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 435,446 IT Pros & Developers. It's quick & easy.

Images not appearing after a page refresh in IE (timeout issue?)

P: n/a
In a monitoring app I have written, the message summary screen
refreshes itself automatically every couple of minutes via the
line <meta http-equiv="Refresh" content="180">.

The screen mostly comprises a table of single-line messages,
and next to each a small status image (red for error, yellow
for warning, etc).

Normally in Internet Explorer these images display fine. But
occasionally, after a refresh, the "missing image" cross and
image title are displayed instead.

This usually happens only with the image displayed (or supposed
to be) most often on the page, typically the green OK button.

Can anyone suggest what causes this problem, and more importantly
how I can eliminate it?

(I suspect the problem is caused by a timeout, in that if IE doesn't
receive a requested image within a certain time then it just assumes
the image is not available. If so, is there any way to increase its
timeout interval, or to ensure the images are kept in IE's cache
across page refreshes?)

Thanks in anticipation.
Cheers

John R Ramsden (jo**********@sagitta-ps.com)
Jul 20 '05 #1
Share this Question
Share on Google+
3 Replies


P: n/a
On Tue, 19 Aug 2003 12:54:32 +0200, "Alan J. Flavell"
<fl*****@mail.cern.ch> wrote:
I've heard rumours that IE makes up its own rules, which would be no
big surprise. Allegedly, when it expires an HTML page, it goes and
expires all the in-lined images too. The theory being that those who
operate MS-sponsored web servers are too stupid to follow the rules of
HTTP, and so MS's client agent has to compensate on their behalf.
Disclaimer: I haven't proved this for myself, it could be a malicious
lie.


I've no reason to suspect this from my experience, IE certainly
revalidates pages distinct from the images in some logs I have access
to here (well the logs just show the html being revalidated and not
the associated resources) however that's not a complete test, but it
shows it doesn't happen always.

The bigger problem with IE, is that it does conditional queries on all
resources which do not have an explicit expires in some settings,
including multiple uses of the resource on the same page or refresh,
Other browsers (and even older IEs) don't do this, they'll only
request once per page in any settings. To overcome this, you must get
a bright green dot with the cacheability engine (unless mnot has fixed
this, a common request when I asked him, but not one he had time for).

Jim.
--
comp.lang.javascript FAQ - http://jibbering.com/faq/

Jul 20 '05 #2

P: n/a
On Tue, 19 Aug 2003 19:56:59 +0200, "Alan J. Flavell"
<fl*****@mail.cern.ch> wrote:
On Tue, Aug 19, Jim Ley inscribed on the eternal scroll:

Then I'd better withdraw the claim.


It could well be true, as I'm not sure I can easily identify if it's
IE choosing to expire the page, it may be different for example with
200 day old content rather than 1 hour old which is more what you can
test easily with, my logs suggested no, which are 30 day expires or
so, and anytime in the last year age.
To overcome this, you must get
a bright green dot with the cacheability engine


Sorry, I didn't quite parse that. Could you clarify please?


Pretty much what I said in the paragraph before, IE requires a
specific expires, even if the message is 2 years old - if it doesn't
have a specific expires it will still be validated, especially nasty
with rollovers etc. where most people make this mistake.
(unless mnot has fixed
this, a common request when I asked him, but not one he had time for).


This was simply related to the fact that the cacheability engine only
provides a lot of its good/bad information by the colour of a blob,
the text can be read to answer the same, but not so readily.

Jim.
--
comp.lang.javascript FAQ - http://jibbering.com/faq/

Jul 20 '05 #3

P: n/a
"Alan J. Flavell" <fl*****@mail.cern.ch> wrote in message news:<Pi******************************@lxplus018.c ern.ch>...
On Tue, Aug 19, John Ramsden inscribed on the eternal scroll:
Jim Dabell <ji********@jimdabell.com> wrote in message news:<HR********************@giganews.com>...

Further reading:

<URL:http://www.mnot.net/cache_docs/>


Many thanks for your reply Jim. I read the reference you gave, but I'm
still slightly hazy about how the HTTP headers allow the browser to
distinguish between a page and the images referenced from that page.


They don't. HTTP headers that come with an HTML page are supposed to
relate precisely to that HTML page, while the HTTP headers that come
with each image are supposed to relate precisely to that image.


Yes but how do I set the HTTP headers separately for a particular image,
and what would be the best values? I presume they can't be specified in
the HTML of the page, because the images are just defined by an <IMG>
spec, and as far as I can see there's no way to tie an HTTP header to
those either individually or collectively.

Is it possible to specify in the HTTPD configuration HTTP headers for
various file name extensions ? I don't _recall_ anything like that from
my studies of Apache for example, but there are so many damned settings
that one can't rule it out!

I do appreciate all the replies so far; but I'm afraid you're talking
way over my head and in what seems like largely vague generalities.

(If c.i.w.a.html is only intended for discussions between experts,
perhaps someone could point me to a forum where specific answers to
questions are more likely to be obtained.)
Cheers

John Ramsden (jo**********@sagitta-ps.com)
Jul 20 '05 #4

This discussion thread is closed

Replies have been disabled for this discussion.