Could you check the Add-ons page? Either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click Extensions. Then on the right side, check for the Yahoo toolbar extension and you should be able to Disable it (or Remove it). Is it listed there? If not, perhaps another extension looks like the Yahoo! toolbar. Hmmm... Often a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Any improvement?