Client-side Image Caching

My understanding of client side image caching is as follows:

1. Images are saved to the /temp directory or whatever directory specified as the temporary internet folder for Netscape 4.x and IE 5.X and 6.X whenever a webpage is accessed with image references as part of the content being transferred to the requesting client.

2. Depending on the browser settings, the browser is supposed to check and see if the image being referenced/transferred already exists, and if so, will use the cached copy of the image in the temporary internet folder.

Here are the questions:

1. Biggest one of all...do I understand the use of the temporary internet folder and it's capabilities correctly.

2. If the image referenced in the requested page already exists in the clients temporary internet folder, why does it appear that the image is not being read from the local folder, but instead goes out to the webserver and obtains another copy. (I'm assuming this is what happens when the urls flash in the status bar of the browser as images are being referenced.)

3. How is the cached image caparison conducted, or how does the client know if a newer version of the same image is available? (byte comparison? timestamp?)

4. Is there a way to force the use of client side cached images?

Any help in this area would be greatly appreciated. Thanks in advance.

As far as I was told:

1. Biggest one of all...do I understand the use of the temporary internet folder and it's capabilities correctly.

>>Yes, that is the theory.

2. If the image referenced in the requested page already exists in the clients temporary internet folder, why does it appear that the image is not being read from the local folder, but instead goes out to the webserver and obtains another copy. (I'm assuming this is what happens when the urls flash in the status bar of the browser as images are being referenced.)

>> The browser has to check for an updated copy, so will go to the server and check. If the version there isn't newer it will not download it. Although it means traffic going back and forth, it's quicker than downloading the file itself.

3. How is the cached image caparison conducted, or how does the client know if a newer version of the same image is available? (byte comparison? timestamp?)

>> URL,filename,timestamp. A byte comparison would take longer than downloading the file, so would be useless.

4. Is there a way to force the use of client side cached images?

>> Not that I know of, if the local settings say don't cache then the browser wont cache, simple as that.

Is there a way to forward the current page to a different URL when the refresh button is hit, using Javascript or something similar?