It appears when you press Ctrl+t or use File > New Tab?

First, make sure you have disabled or removed any Yahoo add-ons here:

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

Next, check what Firefox has for the new tab page in the about:config preferences editor.

(1) In a new tab, type or paste about:config in the address bar and press Enter. Click the button promising to be careful.

(2) In the filter box, type or paste newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter the desired value:

(i) Page thumbnails (default)

browser.newtab.url = about:newtab

(ii) Blank tab

browser.newtab.url = about:blank

(iii) Built-in Firefox home page

browser.newtab.url = about:home

(iv) Any other page

browser.newtab.url = full URL to the page

Press Ctrl+t to open a new tab and verify that it worked. Fixed?

Maybe also check for extensions.

• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Start Firefox in Safe Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

See also:

• [/questions/770771]

I fixed it by deleting anything "yahoo" and a "Freeze" extension/add on!