I've got (actually my employer has) a mobile website that enables Safari integration (for iPhones and iPads) - meaning that customers can bookmark it to their home screen and then it would behave as a standalone web app (no address bar, custom icon, start-up image etc).
It works all right except that one week ago (coincidentally soon after apple has released iOS 6.1.2) some of our customers (6 of them initially) complained that they no longer get the normal content but a '404 page' of a public wifi provider (The Cloud owned by Sky here in the UK). After a bit of investigation we've figured that at some point those customers connected to the Cloud wifi without actually logging in (it's one of those providers that would redirect you to a login page to enter your credentials, after which you can carry on browsing). The thing is that even after switching back to their private wifi or mobile data connection the application would display the Cloud's page.
This only happens (as far as I can tell) when the application is launched via the bookmark (I couldn't see this behavior when using it from safari).
What happens is that the customers would connect to the cloud wifi (without logging in), they would open the application at which point the router will issue a redirect response to their login page; the application would cache the login page and it will always display it whenever using the bookmark again. (I've performed a capture when this happens and there are no requests being made at start-up whatsoever).
Even weirder, in this situation, if removing the existing bookmark and adding a new one will show you the same cached page (with the whole operation being performed away from the Cloud). We've fixed this by adding a unique identifier to the URL each time we hit the bookmark screen (this indicates that the web apps' sandboxes are linked to the url, which is to be expected).
What we're trying to achieve is to have the application properly recovering after the customer has moved away from the Cloud. But there doesn't seem to be a straight forward way to do this.
Furthermore there's a level of inconsistency in all of this - most of the times when the flow is performed I will see a 404 page (a custom 404 page https://service.thecloud.net/service-platform), but sometimes I would be properly redirected to the login page, in which case the application would not break.
My assumption is that there is a weird race condition in the standalone web app application model causing the browser not to properly handle redirects (and actually caching 404 pages). I've raised a support incident with Apple (which eventually turned into a bug report) but it might take a while and I'm trying my best to figure out a workaround.
Any ideas, maybe someone has seen this before? The issue is aggravated by the fact that I need to have a 5 minutes walk ever time I'm testing any fixes; I've tried creating simple test forms, but I wasn't able to reproduce the issue, where as with the full app I can do it pretty much every time.
Here's a summary of the steps to reproduce:
In the end the fix was to add a unique query string parameter with the initial page request (pretty easy with the setup we already had, via the launcher page). I've filed a bug report with Apple which they've acknowledged by linking it to a previous item. Here's a post on the topic: http://blog.onos.ro/ios-6.1.2-caching-issue