Clear Cookies & Cache

• https://support.mozilla.com/en-US/kb/Template:clearCookiesCache

Clear the Network Cache

• https://support.mozilla.com/en-US/kb/How%20to%20clear%20the%20cache#w_clear-the-cache

Troubleshooting extensions and themes

• https://support.mozilla.com/en-US/kb/Troubleshooting%20extensions%20and%20themes

Check and tell if its working.

it took some effort to get it all erased but the "THING" is still there!!!

\

-> Close Firefox (click Firefox button and click Exit)

-> Start Firefox in Safe Mode by Holding down the Option key while starting your Mozilla Firefox application. (If the Profile Manager opens, select a profile and then hold down the Option key again while clicking the button to start Firefox.)

• As an alternate method, go to Utilities (in the Applications folder) and open Terminal, then run:
  • /Applications/Firefox.app/Contents/MacOS/firefox-bin -safe-mode

-> Firefox Safe Mode window will appear -> DON'T SELECT ANY OPTIONS, just click Continue in Safe Mode

Check and tell if its appearing normally without Yahoo while you are using Firefox Safe Mode.

-> Troubleshooting extensions and themes

• https://support.mozilla.com/en-US/kb/Troubleshooting%20extensions%20and%20themes