You may have ad/mal-ware. Further information can be found in this article; https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-caused-malware?cache=no

Run most or all of the listed malware scanners. Each works differently. If one program misses something, another may pick it up.

hello, this sounds like a problem caused by malware that's already active on your pc (there's not much mozilla can do yabout this when the system is already compromised). please perform the following steps:

1. please go to the firefox menu ≡ > addons > extensions & remove any suspicious entries (toolbars, things that you have not installed intentionally, don't know what purpose they serve, etc).
2. also go to the windows control panel / programs and remove all toolbars or potentially unwanted software from there.
3. finally, run a full scan of your system with different security tools like the free version of malwarebytes & adwcleaner, which are specialised in adware and browser hijackers.

Troubleshoot Firefox issues caused by malware

Thank you so much...it was indeed Malware....have rid my computer from it now...thanks once again great advice...