Caching graphics

[Daniel Kaplan]

On my site, multiple pages recycle 90% of the other pages graphics. Mostly
a menu bar up at the top that appears on virtually all pages.

I am probably making a mistake here, but it appears that each page has it's
own cache.

So if Page A loads, I can see the loading of the menu bar (slowness). If
from there I go to Page B, same thing as with Page A. Now if from Page B, I
go back to Page A (but not with the back button, with a menu choice), then
Page A comes up super quick. So am surmising that graphics from Page A is
cached.

So my question is, if I haven't gotten something wrong, can I somehow say,
"cache these graphics for all of my web pages"? Or not?

Thanks ahead,

Daniel

[David E. Ross]

Daniel Kaplan wrote:

On my site, multiple pages recycle 90% of the other pages graphics. Mostly
a menu bar up at the top that appears on virtually all pages.

I am probably making a mistake here, but it appears that each page has it's
own cache.

So if Page A loads, I can see the loading of the menu bar (slowness). If
from there I go to Page B, same thing as with Page A. Now if from Page B, I
go back to Page A (but not with the back button, with a menu choice), then
Page A comes up super quick. So am surmising that graphics from Page A is
cached.

So my question is, if I haven't gotten something wrong, can I somehow say,
"cache these graphics for all of my web pages"? Or not?

Thanks ahead,

Daniel

I believe that caching is not standardized among browsers. Each browser
can (and likely does) do it differently. Thus, some might cache a
rendered page -- HTML, CSS, images, audio, etc combined -- while others
might cache the constituents separately. You want the latter, but this
is controlled by the visitors to your Web pages through their choice of
browsers. The most you can do is indicate NOT to cache:
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
and I'm not really sure this works.
--

David E. Ross
<http://www.rossde.com/>

Concerned about someone (e.g., Pres. Bush) snooping
into your E-mail? Use PGP.
See my <http://www.rossde.com/PGP/>

[Alan J. Flavell]

On Tue, 11 Apr 2006, Daniel Kaplan wrote:

I am probably making a mistake here, but it appears that each page
has it's own cache.

Mistake? news:alt.possessive.its.has.no.apostrophe

But, to your substantive question, I'd advise you to start from
the canonical tutorial for cacheing: http://www.mnot.net/cache_docs/
and to expose your web site to an instance of his cacheability engine
for a report on its properties.

Beyond that, you have to put up with whatever policies the individual
clients apply. Those can differ, but AIUI there's not a lot that one
can do (from the provider side) to make things better - and many
casual attempts to interfere are reputed to make things worse.

You certainly should make sure that your server responds correctly to
an if-modified request. AFAIR his cacheability engine will report on
that aspect, along with the other things that it reports.

hope this is useful

[Michael Winter]

On 11/04/2006 23:12, Alan J. Flavell wrote:

[snip]

You certainly should make sure that your server responds correctly to
an if-modified request. AFAIR his cacheability engine will report on
that aspect, along with the other things that it reports.

A cursory glance at the source suggests that it does, though only the
If-Modified-Since header. Other conditional requests are not tested.

Perhaps when it was written (Feb 2000, according to the Last-Modified
header sent for the source tarball) it wasn't deemed worth checking
other types due to lack of general use, or maybe that he concluded that
support of one infers support of others.

Mike

--
Michael Winter
Prefix subject with [News] before replying by e-mail.

[Jukka K. Korpela]

David E. Ross wrote:

The most you can do is indicate NOT to cache:
Not correct. There's quite a lot one can do in HTTP.
<META HTTP-EQUIV="Pragma" CONTENT="no-cache">
If used inside an HTML document, it has some effect on some browsers as
regards to caching the HTML document itself.
and I'm not really sure this works.

It doesn't, of course. How could that work in an image file?

[hug]

"Jukka K. Korpela" <jk******@cs.tut.fi> wrote:

David E. Ross wrote:

The most you can do is indicate NOT to cache:

Not correct. There's quite a lot one can do in HTTP.

<META HTTP-EQUIV="Pragma" CONTENT="no-cache">

If used inside an HTML document, it has some effect on some browsers as
regards to caching the HTML document itself.

and I'm not really sure this works.

It doesn't, of course. How could that work in an image file?

There is an http "Cache-Control" header. Some browsers honor it,
others don't. I don't really know about other types of caching
forwarders like proxies, I'd assume that they would support the full
http protocol but people throw all kinds of crap out into the
free/open-source world and it all needs to be looked at on an
individual basis. But hell, I still think the GPL and OSF are a
communist plot to destroy the software industry which in conjunction
with M$'s shenanigans has worked, so wtf do I know.

Good luck, keeping your graphics as small as possible is always a good
thing, there are still people stuck on 56k dialup.

--
http://www.ren-prod-inc.com/hug_soft...action=contact

[pegasusflightresources]

Daniel Kaplan wrote:

On my site, multiple pages recycle 90% of the other pages graphics. Mostly
a menu bar up at the top that appears on virtually all pages.

I am probably making a mistake here, but it appears that each page has it's
own cache.

So if Page A loads, I can see the loading of the menu bar (slowness). If
from there I go to Page B, same thing as with Page A. Now if from Page B, I
go back to Page A (but not with the back button, with a menu choice), then
Page A comes up super quick. So am surmising that graphics from Page A is
cached.

So my question is, if I haven't gotten something wrong, can I somehow say,
"cache these graphics for all of my web pages"? Or not?

Thanks ahead,

Daniel

I believe that you can manipulate the template for frames in order to
get what you want, and only have to change a frame instead of reloading
the whole page.

[Alan J. Flavell]

On Wed, 12 Apr 2006, hug wrote:

There is an http "Cache-Control" header. Some browsers honor it,
others don't. I don't really know about other types of caching
forwarders like proxies,
The well-reputed tutorial at http://www.mnot.net/cache_docs/
could bring you up to a reasonable speed on such matters.
I'd assume that they would support the full
http protocol but people throw all kinds of crap out into the
free/open-source world and it all needs to be looked at on an
individual basis. But hell, I still think the GPL and OSF are a
communist plot to destroy the software industry which in conjunction
with M$'s shenanigans has worked, so wtf do I know.
That might be a good summary of your personal position, but I'm not
sure how you think it's going to be useful to the hon. Usenauts who
read your posting.
Good luck, keeping your graphics as small as possible is always a good
thing, there are still people stuck on 56k dialup.

No disagreement there, but it's not the whole story.

Cacheability is also a factor (other than on first access, of course)
if you want reasonable response over any kind of limited channel.
Which can include broadband when it's congested (naming no names...)

Another thing to take into account (especially for those who build
pages with shove-and-click tools without understanding what's under
the covers) is to avoid referencing multiple copies of the same
graphic under different URLs.