Is this in the complete browser or specific areas only? Is your desktop affected by this?

1.) Right-click on the FF Title bar / Customize / There is a zoom control tool there / Drag it to something like the Bookmarks Toolbar

2.) This Add-on provides some additional options . . . Zoom Page WE . . . https://addons.mozilla.org/en-US/firefox/addon/zoom-page-we/

3.) In Win 10, right-click on Desktop / Display settings / Resolution - make it something bigger

You can set layout.css.devPixelsPerPx to 1.0 (default is -1) on the about:config page. Adjust its value in 0.1 or 0.05 steps (1.1 or 0.9) until icons or text looks right. Modifying layout.css.devPixelsPerPx affects user interface and web pages (global zoom). You can use an extension to correct the appearance of web pages.

Doesn't affect my desktop icons and captions. However it has set my login screen really small. It's affecting all my email, any order screen like Amazon or eBay. Resetting zoom level greatly increases the size of the screen, but only slightly on the text. It hasn't affected things like Quicken or Word. Thanks for any help you can give.

Doesn't affect my desktop icons and captions. However it has set my login screen really small. It's affecting all my email, any order screen like Amazon or eBay. Resetting zoom level greatly increases the size of the screen, but only slightly on the text. It hasn't affected things like Quicken or Word. Thanks for any help you can give.

uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Note: your Firefox Profile is saved. But you should make a back up before you do : https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer

Reinstall with Current Release Firefox 57.0.2 with a Full Version Installer https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

Too much to write here. I have put it on a pdf on my Google Docs:

font size . . . . https://drive.google.com/open?id=16QtX6X7gwdYxSHmp8uDa9ZEo_uCe0FYe