You might be surprised when Mozilla Firefox 31 suddenly starts using the Yahoo search provider instead of Google to conduct your searches; and you might be even more surprised to learn that you agreed to this change when you installed a Yahoo program on your Windows 8 computer. The option to make Yahoo the default search provider is selected by default in the setup wizard and you may not notice it if you click "Next" too fast. Solve this issue by changing the default search provider in Firefox back to Google. If the newly installed program changed the homepage as well, change it back to your preferred Web page.
Changing the Search Provider
Locate the small downward-facing arrowhead in the Search box, next to the Yahoo logo. Click it and choose "Manage Search Engines" from the menu. The Manage Search Engine List window displays.
Select the "Google" search engine and then click the "Move Up" button until you position it at the top of the list. The first search engine in the list is the default search engine. To receive search suggestions while typing, check the "Show search suggestions" box. You can remove search engines from the list by selecting them and clicking the "Remove" button. If you accidentally delete a search engine you use, click the "Restore Defaults" button to recover it.
Click "OK" to apply the changes and close the Manage Search Engine List window. Note that Google is set as the search engine in both the Search box and Address box. You can conduct searches using either of these boxes.