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.
Yahoo programs often change the homepage during the setup process. To change the homepage, click the "Menu" button and click "Options" to open the Options window. Ensure the "General" tab is selected and then change the URL in the "Home Page" field. To display the homepage when you start Firefox, select "Show my home page" from the "When Firefox starts" drop-down box, then click "OK."
If you are unable to change the search engine or homepage in Firefox, one of the extensions might be messing with the settings. Remove unnecessary extensions, such as toolbars, from the Add-ons page. To open the page, click the "Menu" button and then click "Add-ons." Remove extensions by clicking the "Remove" button or disable them by clicking the "Disable" button.
If nothing works, you can reset the Firefox program. To perform the reset, click the "Menu" button, click the blue question mark icon and then click "Troubleshooting Information." Click the "Reset Firefox" button and then click "Reset Firefox" to confirm. The Web browser preserves your browsing history, bookmarks, saved passwords, saved forms and cookies.
A reset removes all extensions and themes, custom search engines, plugin settings and toolbar customizations. It also resets all settings to their default values.