Here's a link to read that may help you

https://support.mozilla.org/en-US/questions/1030895

Adchoice or Adchoices?

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Do the ads you're seeing contain clickable icons similar to this?

If you click the leftmost icon does it take you to this Google help page? https://support.google.com/adsense/troubleshooter/1631343

If so, you should be able to block them with "Ublock Origin" or "Adblock Plus" (if you uncheck "Allow some non-intrusive advertising").
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If on the other hand, the ads are not like above... maybe they're being caused by adware?
I'm not a adware person but I think there may also be an adware that goes by the same or similar name. If it were me, I'd probably scan with my primary AV, then Malwarebytes and then AdwCleaner. Like I say though, I don't know much about adware, I'm just stating what I, as a regular user, would probably do.

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Another
thought. If you installed a piece of software around the time you
started noticing the ads, maybe you could use "System Restore" to return
your system to a state prior to when the ads started?

If all the above fail try restarting FF with add-ons disabled to see if your concern continues. If it doesn't you will have to wade through your add-ons to see which one piggy-backed the culprit. I had this happen to me once.

DA

All, thanks for these answers. I'm afraid that I still can't get rid of adchoices on my work computer. Chuggerguy, yes I meant adchoices and they look just like the ad you inserted above. Here's the deal. I have a work computer and a home computer, both running firefox. I'm getting the ads on the work computer but not the home computer. I have Adblock Plus on both computers, and I've unchecked Allow Some non-Intrusive Advertising on both. Yet I'm still getting the ads on the work computer. So I'm trying to figure out why and what else I can do to the work computer to get rid of them. I can't seem to get any help online, nor, sadly, from my work IRT people. If AdBlock Plus is running the same on both computers but it is not blocking ads on one of the two computers than it has nothing to do with Adblock Plus. Yet I don't have any other ad blocker on my home computer. Help?

Try refreshing Firefox as shown below,

https://support.mozilla.org/en-US/kb/reset-preferences-fix-problems