Firefox display a built-in new tab page on new tabs unless it is replaced by an extension. So the fi

Firefox display a built-in new tab page on new tabs unless it is replaced by an extension. So the first stop is, the Add-ons page. Either:

Ctrl+Shift+a (Mac: Command+Shift+a)

"3-bar" menu button (or Tools menu) > Add-ons

type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions. Then cast a critical eye over the list on the right side. Any system extensions that Firefox installs on its own are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or unfamiliar? If in doubt, disable.

Any improvement?

You may also want to check your default search engine setting: Change your default search settings in Firefox. Sometimes there are Yahoo results but someone else's icon when you check your default, like the McAfee M, so be on the lookout for that.