Are you running in full screen? Try pressing the <F11> key.

It's in full screen. F11 decreases sound. It's an imac -- big screen, great speakers, good for films and youtube, otherwise useless. F6 is blank, so I tried that. It gave me enough screen that I could see a double-headed arrow, which I would think means full screen, but I clicked on it anyway, and the toolbar and bookmarks appeared, so I guess it means exit full screen. Thanks for the tip, Fred. Problem solved till next time. It started with Firefox’s familiar “Well, this is embarrassing” error message. I'll keep this info secure on my dependable PC laptop, which I'm using for this discussion.

On Mac you can toggle Full Screen mode with Command+Shift+F).

• https://support.mozilla.org/kb/how-to-use-full-screen

Glad to help. Safe Surfing.

Thanks, cor-el. I'll try that next time. It all seems so simple when you know what you're doing. You people are a lifeline.