Is it in the toolbar area? You may have an unwanted extension such as "Default Tab". Try this: Disable ALL nonessential or unrecognized extensions on the Add-ons page. Either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click Extensions. Then, if in doubt, disable. Usually 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. Can you track down the culprit? Note: You might need to remove it through the Windows Control Panel, Uninstall a Program, if there's no Remove button on the Add-ons page for it.