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View Full Version : "Prefetching is not allowed due to the various privacy issues that arise."


sauce
Oct 29, 2008, 07:58 AM
Prefetching is not allowed due to the various privacy issues that arise.

I am connecting through a squid proxy server. I had to disable my proxy to be able to use this site.

bstreiff
Oct 29, 2008, 08:24 AM
I'm connecting through squid, too, and I don't have any problems.

Of course, mine's just set up to do transparent caching of pages I do view-- as opposed to looking at pages I do view, then grabbing every page off of that one, a small fraction of which I'll view. (and consuming server-side bandwidth in the process).

Doctor Q
Oct 29, 2008, 11:12 AM
I am connecting through a squid proxy server. I had to disable my proxy to be able to use this site.
The likely explanation is that the proxy server was doing pre-fetches that our forum software was blocking when you were logged into the forums.

Other reasons the message can show up: If you are using Firefox or another Mozilla-based web browser, the pre-fetches it does can be a problem. To avoid it, you can use about:config to set network.prefetch-next to false. The Google Toolbar can also reportedly be the source of the problem.

As I understand it, here's what's going on:
Some web browsers and proxies pre-fetch web pages, essentially "clicking" links on a page you view and saving the results so that you get fast results if you click that link yourself. That was also the idea behind Google Web Accelerator.

A problem can occur if a page shouldn't be pre-fetched. For example, you don't want a background process to pre-fetch the page you get when you click a "Cancel" button while you are on a transaction page of some kind. It's unlikely to be an issue on a public web page, where links usually produce read-only results, but on a site where you log in and can change server-side information (posting in a forum, for example), clicking every link to pre-fetch the results isn't a good idea.

There's also the issue of privacy. If you log into a web site, you may not want a cache on a server somewhere to save pages that only you should see.

A server-side application can try to avoid these problems by including hints about pre-fetching. If it does not do this, or if the proxy, web browser, or other client-side application ignores the hints, inappropriate pre-fetches can result. vBulletin, our forum software, has code to address the problem by detecting and blocking pre-fetches from Mozilla-based web browsers, when you are logged in. But it should be blocking only background (automatic, invisible) fetches, not the main web page you are trying to view, so you should not be seeing an error message. That leaves the question of what conditions result in the message and the implications for proper proxy configuration.