I like this for board footage

[terrifictimbersllc]

I browsed to the calculator on my phone. Then I turned my phone to airplane mode.   Then I went back to the open page in my browser (Safari), used the calculator successfully.

It is "saved" among the open windows in my phone's memory.  Unlike other open windows where the links don't work when I'm not connected to the internet, the poke calculator's poker buttons and calculator functions DO work when I am not connected to the internet.   So to "save" it, I have only to leave this window open and not overwrite it by browsing somewhere else with that window. 

[Jeff]

Found this for iPhone.

 You can read the webpage later, even if you're offline. To save articles offline, go to Settings > Safari > Reading List and tap Automatically Save Offline. If you ...

[LeeB]

You can still get internet via wifi in airplane mode. You just can't get cell reception. 

You can use airplane mode to avoid roaming charges when travelling. You won't be able to send or receive text messages or phone calls, or use data services, butyou could connect to a Wi-Fi network to check your email or browse the Internet.

[alanh]

Found this for iPhone.

You can read the webpage later, even if you're offline. To save articles offline, go to Settings > Safari > Reading List and tap Automatically Save Offline. If you ...

OK, got it, thanks!