It's a sneaky little devil as it seems to wait a few seconds to cover up what you're typing, just long enough for you to think you're safe. Having boxes, etc., pop up while you're working is just wrong. I'm guessing that the designers at Adobe don't ever edit web pages, or this would have been disabled long ago.
Anyway, to disable it on a Mac, click command+option, and a box appears and you can click another little box that says *disable*.
It does have a tendency to come back as you move around the page. Just repeat the process to disable it. I wish they wouldn't do this stuff, but they do!
For Windows, see the comment below by +Brian Johnson. Thank you, Brian!