Thanks, I see this behavior too. Interestingly enough, there's nothing on the page itself that can cause this behavior, this is all due to the sample calculator app embedded in an iframe element.

We use the HTML5 History API to ensure that we can go "back" in an app which is run as a standalone app on Android when the system back button is pressed -- and there really isn't another way to go about it. (Not having the system back button go back would lead to a pretty terrible user experience when calculators are run as standalone apps.) However, we'll want to disable this behavior whenever apps are embedded in web pages -- I'll have a look at this later tonight.

Again, thanks for reporting the bug!

This issue should now be fixed. Thanks again for reporting it!