You may have ad / mal-ware. Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up. ------------------------- 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.newtab.url''' This tells Firefox what to show when a new tab is opened. If you want, right click and select '''Modify'''. You can change the setting to; '''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. The same instructions are used for the new window setting, listed as '''browser.startup.homepage'''.