hello, this sounds like a problem possibly caused by adware on your pc. please go to firefox > addons > extensions & remove any suspicious entries (toolbars, things that you have not installed intentionally, don't know what purpose they serve, etc). also go to the windows control panel / programs and remove all toolbars or potentially unwanted software from there and run a full scan of your system with the security software that you have in place and different other tools like the free version of malwarebytes & adwcleaner.

Remove a toolbar that has taken over your Firefox search or home page Troubleshoot Firefox issues caused by malware

Dear Sirs, my name is Simone and i have a question: I would really appreciate to remove Value Apps from my firefox browser and i don't know how to find the place mentioned above from you (i mean:the "addons button".) Would you pls show me how to do it, since i can't stand appearing in my bar, a piggy bank on it with paper money sticking out of it. I want it gone Please !!?? Many thanks for the help. I may have done some mistakes with the language since i'm Brazilian having it as my mother language. Thanks a lot ! my email: monefassbender@gmail.com.

Try Junkware removal tool, it will remove Value Apps and associated adware.

http://deletemalware.blogspot.com/2013/06/remove-value-apps-pop-up-removal.html

You may also use AdwCleaner.