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 free to use malware scanners. Each works differently. If one program misses something, another may pick it up.

Thanks for the reply ran Malware (prem) says no problems. Does the IP tell us anything?? Cheers

https://www.bing.com/search?q=who+is+139.45.196.72

Thanks again but how can I stop Firefox trying to connect to that site when I haven't even opened the browser? Cheers

I called for more help.