Hello David
Thanks for these links, and the tip.
So, comparing the responses to my questions about
caching, and comparing my own experiences from
testing at home, and testing from external sites,
I had begun to find a great deal of inconsistency
in how IE6 caches. This is true even when all
relevant IE6 settings are the same. True even when
using the same test machine (laptop: XP/IE6)
from my CableModem broadband at home and from
remote sites.
It seems (but can not say definitively), that among
the factors, response time of the issueing site
is important. I was comparing my site at home
(Compaq AMD Athlon 3000 / Fedora Core 1 / tomcat 5.0.28
/ cablemodem broadband with max upload speed of
70 Kbytes/sec, max download of 700 kbytes/sec)
with www.smugmug.com (whom I presume use apache/PHP
from a server farm on a commercial high-speed line).
At home, their stuff, and my stuff both cache in IE6
perfectly: not the slightest ripple or flicker when,
say, prev or next'ing through images accompanied by
a group of thumbnails which only change every 12 or 15 pix.
But from external sites (hotel room, a neighbors house
who has DSL, etc) both smugmug and my stuff will occasionally
reload images or just flicker for an instant (looks like
an invisible breeze blew across the screen).
And this is particularly noticeable when the response times
are inconsistent at these locations external to my house.
So I have conjectured that delays in response time to my
browser can play a role.
Another interesting discovery: the following javascript
invocation of a IE specific routine helped a great deal:
filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(enabled=true,
sizingMethod=scale src='/image/pngfix.png')
Without this, virtually every reload on IE6 (when I am
testing at home) causes a flicker to run through the browser
screen (not a true reload of the images, just the merest
flicker, but still annoying to the viewer). Note that the
actual png file indicated isn't even present.
I know: the above call should only affect png files, and here
we are talking about only jpg and gif files. I got this
out of the smugmug pages. It was the only technically different
thing that I could see in their stuff, and when I put it into
my pages, voila: perfection, at least at home (where my
response times are virtually instantaneous).
So anyhow, I write all this just to begin to give you a feeling
for how complex this issue of caching of images really seems
to be. Evidently, many factors.
Thanks again for the tips that you sent. I will try everything.
Maurice Yarrow
David Rees wrote:
On 10/27/05, Maurice Yarrow <[EMAIL PROTECTED]> wrote:
(For Internet Explorer:)
Do you happen to know which are the "right headers" to set,
especially for images ?? If not, maybe you could point me
to a good source of info for caching rules for IE.
Use these links for further reading:
http://www.mnot.net/cache_docs/
http://www.mnot.net/cacheability/
The tips apply to all browsers, whether or not running under SSL. Of
course, depending on the browser, when under SSL the browser may or
may not cache items across restarts of the application.
The header that most often is missing which greatly aids caching is
the Expires header.
-Dave
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