Caching when "save encrypted pages to disk" is disabled

Hi.

We're having trouble with a web application that is served over SSL. The
application GUI contains a dynamically created "tab bar" at the top; the
className attributes of the tab elements are changed onmouseover/out.
The CSS classes contain background-image properties, and at the moment
we're unable to tell IE7 to take the images from the cache. Every time
the mouse moves over (or away from) a tab, a new request is sent to the
server. This causes a very noticable slowdown, and a brief moment where
the tabs don't have any background image at all.

The problem disappears when the the "Do not save encrypted pages to
disk" preference is disabled. Unfortunately, this option is enabled
company-wide (via policy settings, I believe), because otherwise PDF or
Excel downloads don't work properly. I don't know what the deal is with
the PDF downloads, or how that is connected to this setting, but the
company admin demonstrated the effect to me with a different application
served from the same in-house server - clicking on a link to a .pdf file
did nothing at all when "save encryped pages" was enabled.

I've played around with the HTTP headers, but couldn't find a way to
solve the problem. Here's what I send with the image files:

Expires: Tue, 01 Dec 2009 12:00:00 GMT
Last-Modified: Mon, 15 Dec 2008 12:00:00 GMT
Cache-Control: post-check=86400, pre-check=86400
- or -
Cache-Control: no-check=86400

Preloading the images in a hidden div will work, but is obviously not
very efficient (every page request would load the same ~60 small
graphics again).

Is there any way at all to persuade IE7 to cache these images?
Can they be cached between page loads?
And why doesn't the memory cache work when "save to disk" is disabled?
Is the "don't save encrypted pages" option really necessary to enable
proper PDF and Excel downloads?


Any help would be greatly appreciated.


- Conrad

On 2008-12-18 03:43, Conrad Lender wrote:
> We're having trouble with a web application that is served over SSL. The
> application GUI contains a dynamically created "tab bar" at the top; the
> className attributes of the tab elements are changed onmouseover/out.
> The CSS classes contain background-image properties, and at the moment
> we're unable to tell IE7 to take the images from the cache. Every time
> the mouse moves over (or away from) a tab, a new request is sent to the
> server. This causes a very noticable slowdown, and a brief moment where
> the tabs don't have any background image at all.
> [snip]

Just a follow-up for the archives (judging from the lack of a response,
I think I may have posted to the wrong group). We've not been able to
reliably get IE to cache images without the "save encrypted images to
disk" setting. Instead we've resorted to rather drastic measures in
order to reduce the number of requests, including merging most of the
small images into CSS sprites, and concatenating and minimizing scripts
and stylesheets.

Still not sure about what forced the admin to turn off the cache, or
what the problem with the PDF files was.


- Conrad

"Conrad Lender" <crlender@yahoo.com> wrote in message news:h9ednd43eKYdkNbUnZ2dnUVZ_j6dnZ2d@supernews.co m...
> On 2008-12-18 03:43, Conrad Lender wrote:
>> We're having trouble with a web application that is served over SSL. The
>> application GUI contains a dynamically created "tab bar" at the top; the
>> className attributes of the tab elements are changed onmouseover/out.
>> The CSS classes contain background-image properties, and at the moment
>> we're unable to tell IE7 to take the images from the cache. Every time
>> the mouse moves over (or away from) a tab, a new request is sent to the
>> server. This causes a very noticable slowdown, and a brief moment where
>> the tabs don't have any background image at all.
>> [snip]
>
> Just a follow-up for the archives (judging from the lack of a response,
> I think I may have posted to the wrong group).


Try the MSDN web forum for IE web development.


> We've not been able to
> reliably get IE to cache images without the "save encrypted images to
> disk" setting. Instead we've resorted to rather drastic measures in
> order to reduce the number of requests, including merging most of the
> small images into CSS sprites, and concatenating and minimizing scripts
> and stylesheets.
>
> Still not sure about what forced the admin to turn off the cache, or
> what the problem with the PDF files was.
>
>
> - Conrad