If Firefox opened to a page while it was closed, it usually indicates that an external program sent Windows a URL to open in your default browser. This is easy to test by selecting another browser as your default browser, and watching whether the unwanted pages open there instead of in Firefox. The URLs that are opening could be sent by a program that wants to display an advertisement or other notification, or in some cases it could be unrelated to what you're doing and triggered by another event, for example, the time of day. In some past threads, users discovered tasks to launch URLs in the Windows Task Scheduler. For example: * [https://support.mozilla.org/questions/967667 How can I keep Firefox from opening a window to website tofushopnews.com] * [https://support.mozilla.org/questions/965048?page=2#answer-461509 How do I get rid of sponsorship tabs that open automatically?] In Windows 7, you access the Task Scheduler using: Start button > Control Panel > System and Security > Administrative Tools > Task Scheduler Not sure about Windows 10...