My laptop computer keeps going smaller & smaller in type. Now it is about 3 or 4 type size. How do I enlarge?

Am I in the right category: Programming & Design?

I am using this laptop that I bought a year ago so my desktop can do some Malwarebytes & Avast ! virus detection.

I have Windows 7 or Vista on that laptop. I think.

While I am in my email account on a Mozilla Firefox browser, my right hand was resting on the right side of my cursor & right click button.

My type size on the email I was reading got smaller & smaller till I lifted my hand up.

The cursor was over on the right side of the screen.

I used to know how to fix this but FORGOT. I'm almost 65, and don't use that option much anymore.

I tried lowering the screen resolution but that did not work. I tried using Explorer browser but that did not work either.

I tried Control Z and Control X, I tried using the "Arrows" to move the Firefox browser back. I tried screen resolution to 1026 X 766 or something like that but it did not work.

What do I need to do. Thank you.