Marty...
(Done any good reading lately)
Just tested athird4th* browser - MS Edge. That makes 4 that work with Ctrl + and -
AND Ctrl-Scroll wheel (you didn't mention Ctrl with Scroll wheel).
HOWever, if you want to go into nuts-and-bolts you could check the settings on
your browser. I won't go into it now, but if you are using FFox and you want to know, let
me know...
* Can't count!
Also - when you're using the number pad, make sure it is "ON". Often, mine goes OFF
(due to power saving and weird things happen.