Open Settings and the first thing is Startup with tick-box to "Open previous windows and tabs." Make sure that isn't ticked.

Also make sure that you close Firefox before you shutdown the computer and not let Windows close Firefox as that will make the OS reopen Firefox with the previous session. See also: *https://support.mozilla.org/en-US/kb/restore-previous-session You can look at this pref in <b>about:config</b> to set the startup page, use '1' to start with the homepage. * browser.startup.page<br>[0:blank; 1:home page; 2:last visited page; 3:restore previous session] *https://support.mozilla.org/en-US/kb/about-config-editor-firefox