Browsers cache

Question about browser and proxy cache

[maurocanzian]

Getting a page from the browser's cache,
does the site webserver register any hits?

How do Mozilla and Explorer caches work?
Do they compare the cached file with the remote file's http header by a HEAD request?

How does proxy servers manage this matter?

[Dijkgraaf]

As I understand it usually the browser will isue a request with the If-Modified-Since header set to the last datetime the page was fetched, the web server will respond with a 304 (not changed) if the page hasn't changed since that datetime, and then the browser will used the cached version. So yes, you will see this hit in your log with a status of 304.

However, if you put a proxy server in the way all bets are off. The proxy server will sometimes decide that it doesn't need to pass on the request and will itself decide to pass back a page it has cached.
I've particularly noticed this with IE and MS-Proxy server.

Also if a user uses the back button, it will usually used the cached version, unless the page has expired (has an expiry date set that has now passed).

[maurocanzian]

What you have written is it true for both Mozilla and Explorer or do they treat in different way the cache matter?

Thanks

[Dijkgraaf]

In my experience, at one point an IE browser going though a MS-Proxy would behave differently to a Mozilla browser like Netscape going through that same proxy. IE would sometimes not get the latest version even when you pressed Ctrl+F5, however I haven't tested that out lately to see if it is still the case.
Other than that I'm not aware of any difference.
Anyone else know any difference currently?