Thunderbird blinking browser notice -

[Bob Goodwin - Zuni, Virginia, USA]

This is Fedora 22, 64 bit, XFCE, etc. with Thunderbird 38.0.1

When I click on a URL in an e-mail message it immediately starts a 
blinking browser notice at the top left. I know, I've just selected a 
URL and don't need that annoying/distracting box. It's as though I am 
being implored to go look at it immediately but I would like to continue 
reading messages before doing so.

Does anyone know how to eliminate it or at the least stop the stupid 
blinking? Google hasn't helped me ...

Bob

-- 
Bob Goodwin - Zuni, Virginia, USA
http://www.qrz.com/db/W2BOD
box10  FEDORA-22/64bit LINUX XFCE