Text suddenly goes way big
This happens rather often: I’m reading something in Safari/Google or an attachment in Mail and the image suddenly goes way too big.
To return things to normal, I have to hit command/0 -- as in zero. (Hey, it just happened now writing this!)
Please tell me what's going on and if there's a way to stop this.
Fortes
iMac (Retina 4K, 21.5-inch, Late 2015), OS X El Capitan (10.11.4)