Older versions of Firefox (one of which I still use, on my other computer) used to apply text size settings to all sites. If I made the text bigger in order to read one page, it would stay big till I changed it, no matter where I went.

I'm surprised to find that the newest Firefox remembers text size settings separately website by website. If I make the text big (or small) at site A, site B won't be affected but when I come back to site A later, it'll go back to the text size that I set it to before.

suzzie, it sounds like your browser was faithfully remembering that you'd somehow, accidentally or otherwise, switched PC (only) to a smaller font.