HOW.. do I stop computer saving web addresses in the address bar?

So i logged into facebook this morning and it said 6 hours ago (5am) that i'd sent these messages to my friends in alphabetical order. But then it stopped at the letter C. The message to all these people was the same "yourfreedomonline. info these people are making some extra money online pretty neat" What should i do? i use Mozilla Firefox, i've changed my password, but how do i know if my facebook has been hacked or it has a virus? Thanks.  


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