Type '''about:preferences#general'''<enter> in the address bar. There are two settings; * '''When Firefox Starts''' When the browser is started, what do you want to display. Many of us choose '''Show My Home Page.''' * '''Home Page''' When a new page is opened, what do you want displayed. # '''Use Current Page'''. Use what ever page(s) are open at that time. # '''Use Bookmark''' # '''Restore To Default.''' about:home shows a Mozilla home page with tools. You can use any of these that you wish; '''about:home''' (Firefox default home page), '''about:newtab''' (shows the sites most visited), '''about:blank''' (a blank page), or you can enter any '''web page''' or '''about:''' page you want. ----------- '''https://support.mozilla.org/en-US/kb/how-to-fix-preferences-wont-save''' Note: Some software, like Advanced SystemCare with Surfing Protection, can protect files in the Firefox profile folder against changes. If you have such software then check the settings or uninstall this software. ---------- You may have ad / mal-ware. Mac Malware Scanners https://discussions.apple.com/message/29938930#29938930 You can also try https://www.malwarebytes.org/antimalware/mac/index.html