Try disabling or removing the add-on here:

orange Firefox button or classic Tools menu > Add-ons > Extensions category

ty jsher for the answer, although it appears i did not get the whole answer; which extenrion needs removing pls? with kind thanks. rené.

I think you said this was caused by a Facebook chat add-on. Try disabling or removing it.

ok yes that makes sense and i will attempt that, :-) many thanks for your reply jscher, :-), regards, rené.