Hello, Please follow the following:

• At the top of the Firefox window, click on the Firefox button, and then click Add-ons. The Add-ons Manager tab will open.
• In the Add-ons Manager tab, select the Extensions or Appearance panel.
• Select the add-on you wish to remove.
• Click the Remove button.
• Click Restart now if it pops up. Your tabs will be saved and restored after the restart.

Please report if it helped ! Thanks!

I had already done all this and when I go to the Add-on manager it does not show the extension listed anymore, but it still takes me to Yahoo when I click a blank tab. I believe that somewhere in the internal workings of Firefox that the Yahoo extension saves a setting telling it to go to this page when I click a new tab and when you remove the Yahoo extension it is not updating this information.

Hello,

The Reset Firefox feature can fix many issues by restoring Firefox to its factory default state while saving your essential information.
Note: This will cause you to lose any Extensions, Open websites, and some Preferences.

To Reset Firefox do the following:

1. Go to Firefox > Help > Troubleshooting Information.
2. Click the "Reset Firefox" button.
3. Firefox will close and reset. After Firefox is done, it will show a window with the information that is imported. Click Finish.
4. Firefox will open with all factory defaults applied.

Further information can be found in the Refresh Firefox - reset add-ons and settings article.

Did this fix your problems? Please report back to us!

Thank you.

Well... this did clear the problem, but I had to reconfigure Firefox and was unable to get it back the way I had it... so, found instructions on how to restore my old firefox data by creating a new profile, deleting all the new info and copied the data from my "Old Firefox Data" folder and went back to my original settings, which included the new tab always going to Yahoo problem. Kept searching for solution online and found instructions on how to reset the NewTab option in the config file... here are the steps that were much easier and less painful that doing a total reset of Firefox. All I had to do was reset the newtab option:

"manually reset the new tab page by entering about:config into the firefox location bar (confirm the info message in case it shows up), searching for the preference named browser.newtab.url and right-clicking & resetting it to its default value (about:newtab)."

This worked perfect and got me what I needed and firefox is back to normal for me with all my add-ons, extensions and prefrences sill in place.

@BSLewis. Many thanks. This solved the problem for me.