Hi, try this: Type about:config into the address bar, press Enter, accept the warning, scroll down to browser.newtab.url and make sure 'Value' is set to about:newtab (right click > Modify, to change it if necessary, taking care not to alter anything else). If you want something other than the default New Tab page, just enter its URL instead of about:newtab. You may then need to restart Firefox. More - Configuration Editor for Firefox.

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Type about:addons<enter> in the address bar to open your Add-ons Manager. Hot key; <Control>(Mac:<Command>)<Shift> A)

In the Add-ons Manager, on the left, select Extensions. Remove yahoo Anything. Now do the same in the computers Programs Folder.

Windows: Start > Control Panel > Uninstall Programs. Mac: Open the "Applications" folder. Linux: Check your user manual.

After the problem is fixed, Bookmark and use this; Download the Mozilla Search Reset {web link} This add-on is very simple: on installation, it backs up and then resets your search preferences and home page to their default values, and then uninstalls itself. This affects the search bar, URL bar searches, and the home page.

If you discover that a particular extension is causing this problem, please post back and name names for the benefit of others.