Jean-Christian Imbeault wrote:

> I did as you suggested and hit the refresh button on N7. The .gif did 
> *not* display. I guess that is the proper behaviour?

Hmmm. Only if the image referenced in the HTML did not exist. It should 
have simply fetched the fresh resource (image).

> I know the browser probably checked with the server to see if the php 
> page was still valid (and found it was), but do browsers normally 
> check to see if the images in the HTML are still valid too? 

When a browser discovers an image tag in the HTML document, it issues a 
separate request for the image. It is exactly the same as if you had 
typed in the URL to the image in your browser's location bar. As far as 
caching is concerned, the type of content (text, html, image, etc.) does 
not affect caching. There are specific headers that do that.

> Either way that does not answer my question as to wether the image had 
> been cached in the first place. All I know is that the browser did not 
> use a cached copy of the image (possibly because the server told it 
> the gif was no longer available).
> How can I test that the image *was* cached, *and* that the cached copy 
> is used when it the server's version has no been changed? 

The only way to be certain would be to view the HTTP communication 
between your browser and the Web server. Do you have a way to do this? 
My guess is that the browser will issue a request for the image anyway, 
but the server's response is a 304 Not Modified or whatever.


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