Does it make any difference if you turn "full screen" view on and off? The keyboard shortcut for that is F11. In full screen view, Firefox should block the Windows Taskbar, but in regular views, it shouldn't.

That only helps temporarily but it does work. Any other ideas? :)

It only helps temporarily because... Firefox switches back to full screen by itself? What's the sequence of events that brings the problem back?

F11 makes it full, another F11 makes it "normal" and at that point the taskbar appears. But as soon as I go to another program and then shift back to Firefox, I have to hit F11 again. Way too much work!  :D

F11 makes it full, another F11 makes it "normal" and at that point the taskbar appears. But as soon as I go to another program and then shift back to Firefox, I have to hit F11 again. Way too much work!  :D

Hmm, I don't know why Firefox doesn't hold its position when you switch windows. Sometimes the settings file that stores window dimensions becomes corrupted with nonsensical values. You can rename the file and have Firefox rebuild it. Here's how:

Open your current Firefox settings (AKA Firefox profile) folder using either

• "3-bar" menu button > "?" Help > More Troubleshooting Information
• (menu bar) Help > More Troubleshooting Information
• type or paste about:support in the address bar and press Enter

In the first table on the page, find the Profile Folder row, and click the "Open Folder" button. This should launch a new window listing various files and folders in Windows' File Explorer.

Leaving that window open, switch back to Firefox and Exit, either:

• "3-bar" menu button > Exit
• (menu bar) File > Exit

Pause while Firefox finishes its cleanup, then rename xulstore.json to something like xulstoreOLD.json. If you see a file named localstore.rdf, it's ancient now, you can delete it.

Start Firefox back up again and it should use the default window sizing. Any improvement?

This mini-reset will hide the menu bar and bookmarks toolbar. You can use one of these methods to show the toolbar list and select the desired bars there:

• right-click (on Mac Ctrl+click) a blank spot on the tab bar (or the "+" button)
• (menu bar) View > Toolbars
  On Windows, tap the Alt key or F10 to activate the menu bar temporarily.
• in Customize mode > Toolbars button (see: Customize Firefox controls, buttons and toolbars)

To turn on the Bookmarks Toolbar, Menu Bar, or other bars, click it on the list.