back-forward-during-alert-2.html   [plain text]

function loaded()
   alert("While this alert is showing, two-fingered swipe back using a MacBook trackpad, Magic Trackpad, or Magic Mouse.  You should not be able to navigate back.  If you can, dismissing this dialog will likely result in a crash.");

<body onload="loaded();">
Follow the instructions in the alert that shows up on page load.