Usually a toolbar is generated by an extension. Can you find and either disable or remove the Yahoo! toolbar extension from this screen:

orange Firefox button (or Tools menu) > Add-ons > Extensions category

Any luck?

Yes, "Yahoo" default search can be difficult to remove as most people report back that no matter what they do, "Yahoo" returns as a default search tool. Frustrating, we want our "Google" back!

Try this...Upper left, click the orange "Firefox" tab or "help" from the menu bar, from there click on "Troubleshooting Information", then click on the button "Reset Firefox to its default state" (don't worry, bookmarks, etc, will not be affected).

Ahhh, "Google" is back as the default search engine.

The Firefox Reset feature does remove some customizations, as described in this article: Refresh Firefox - reset add-ons and settings. A folder will appear on your desktop named Old Firefox Data. I recommend retaining this folder for a few weeks in case you need to rescue anything from your old settings.

On the Mozilla browser Click on Tools--> Add-On , then you can see Yahoo Toolbar option. Click Remove.

Thats it toolbar is gone.

Regards, Rai

IIRC Yahoo may sometimes provide a Yahoo version of Firefox. Some users may encounter Yahoo toolbars because they have a Yahoo version of Firefox installed.

If anyone is doing any uninstalling please note NOT to use options that remove personal settings, because that will destroy bookmarks and passwords.

In order to uninstall a possibly unwanted extension, please do the following:

1. From the Firefox window click the Firefox button at the top left and select Add-ons, or, if the Firefox button is not shown, click the Tools menu and click Add-ons.
2. Once the Add-on Manager has opened in a new tab, click the Extensions button on the left side of the window.
3. You should now see a list of your installed extensions on the right side together with buttons on the right side of each extension.
4. To remove an extension from Firefox, simply click the Remove button. You should see a message that informs you about the successful removal of the add-on.
5. Note that some add-ons require a Firefox restart to be removed completely. To perform a Firefox restart after the add-on removal, click the Restart now link in the message.

You can find further information about uninstalling extensions in the following articles:

Disable or remove Add-ons

Remove a toolbar that has taken over your Firefox search or home page