The Windows 7 task bar? If you mouse over the bottom of the screen does it reappear? If so, auto-hiding is turned on. Right-click the task bar, choose Properties, and uncheck the box for auto-hiding.

If this only happens in Firefox, you might be accidentally going into full screen mode. The F11 key switches between full screen and normal views.

Does any of that help?

Thank you for your help, but it did not solve my issue. I had already checked the "auto-hide" and it is NOT on. Also, I locked the taskbar, but it didn't keep it from disappearing. I NEVER go near F11. I tell you, it is the gremlins! lol

This has been happening for several months. I tried to rack my brain the first time it happened to see if I did anything different, but could not come up with an answer. It just appears, then disappears! Any other ideas?

Also, another thing began happening last week. I have noticed this only happens when I'm in email. The start button moves up 4 inches on the screen, and that much of the screen is black, all my icons disappear at that part of screen, and about 4 inches of the right side of my screen is black also, and those icons go too, but the gadgets move over to the left over remaining icons! Thanks for any help you can give.

Now I have my taskbar back up. My security had done a scan. Maybe if I run a scan every time the taskbar disppears it will reappear!

Try to disable hardware acceleration.

• Tools > Options > Advanced > General > Browsing: "Use hardware acceleration when available"

If disabling hardware acceleration works then check if there is an update available for your graphics display driver.

• https://support.mozilla.org/kb/how-do-i-upgrade-my-graphics-drivers

Did the above and it did not work. So didn't do the graphics drivers upgrade. Thanks, anyway.

I had accidentally gone into full screen mode. Right click to discover whether you have, then deselect...