Dan,

          I get nothing that announces "Alert" when I navigate through to that page and I did not interrupt NVDA speech at all to be certain that I didn't cut this off before it might have occurred.  At first I had an operating theory that it might be ads that are creating these alerts, but even when I turned off Adblock Plus I still do not get them on that page when it loads in the latest version of Chrome (v 53.0.2785.143 m).

          If you have not scanned your machine recently with a malware detector such as Malwarebytes and/or a spyware detector such as Super AntiSpyware I would suggest you do so.  I had fully expected to hear what you're hearing and have visual elements popping up that correspond to same, but am not.  Just the generic nature of the message, "Alert," makes me wonder if you might have an infection of some kind.
--
Brian

Here is a test to find out whether your mission in life is complete.  If you’re alive, it isn’t.

    ~ Lauren Bacall