Type about:config<enter> in the address bar. If a warning screen comes up, press the Be Careful button. At the top of the screen is a search bar. Type browser.startup.homepage.

Click on this to edit. Look for |about:preferences#general or |about:preferences and remove it.

This can happen if you click "Use Current Page(s)" to set the home page and about:preferences is open in a tab. You can pin the tab with the about:preferences page via the right-click context menu of the tab to prevent including about:preferences to the home page setting if you want to use this button in "Options/Preferences > General". To set a single page as the home page you can drag the globe/padlock to the toolbar Home button.

Firefox uses a vertical bar ('|') to separate multiple home pages.

• https://support.mozilla.org/kb/How+to+set+the+home+page

I just clicked the menu, chose "Options", and in the startup page box deleted the words "about:preferences" from the end of the address. Worked fine and easy to do. If you mess up, just open the page you want to start with and choose "Current Page" again.

Glad to help. Safe Surfing.