how do I get rid of the occasional "Google translate – View this page in …" on top of a page?

I am not sure, when and how often it happens, but once in a while, this suggestion gets displayed on top of a web page within Firefox.

I don't need it, I don't like it, I would like to get rid of it, but I can't find a way.

Update:
Of course I know, apparently I can decide to determine to not get translated web pages in a specific source language. But I am quite sure, I already decided and determined that more than once, when this "Google translate …" appeared on top of a page. So, why don't they respect my decision "for ever"?!?