[LINK] RFI: How Does the Do-Not-Cache Instruction Work?

[Roger Clarke]

A question expressed from the user perspective:

With some web-pages, I can't do a save of the page, nor of images 
within the page.  If I want a copy, I have to do a screen-scrape.

So, if I come back to the web-page later, even a short time later, 
the page and the images are fetched all the way from the web-server 
again.

How does this work?

Presumably something in the HTTP response from the server via the 
ISPs to my browser tell the proxy-servers and my browser not to cache 
anything?

Most, maybe all, search-engine bots do appear to actually respect 
robots.txt clauses.  So maybe proxy-servers and browsers respect the 
requests that travel with web-pages?

Or do some browsers break the rules and cache the contents on my machine?

And do some ISP's proxy servers break the rules and cache the 
contents on their machines?


[A pointer to an explanation that's not heavily technical would be great.

[A pointer to the documentation and a suggestion that I RT(R)FM - 
read the (right) f------ manual - would be fine too.

[Thanks Link Institute!

[Yes, I have an actual and urgent need.  And it's not a consultancy gig.


-- 
Roger Clarke                  http://www.anu.edu.au/people/Roger.Clarke/

Xamax Consultancy Pty Ltd      78 Sidaway St, Chapman ACT 2611 AUSTRALIA
                    Tel: +61 2 6288 1472, and 6288 6916
mailto:Roger.Clarke at xamax.com.au                http://www.xamax.com.au/

Visiting Professor in Info Science & Eng  Australian National University
Visiting Professor in the eCommerce Program      University of Hong Kong
Visiting Professor in the Cyberspace Law & Policy Centre      Uni of NSW