When do you get such a link?
Are you opening Facebook via a bookmark?

That can happen if you click a Facebook link on a specific page.

Such GET data may get appended to show the origin (referrer) of where you clicked the link to open Facebook.

If you have that link bookmarked then you can edit the location and remove that data.

Not opening Facebook from a bookmark. It appears as soon as I click anything on the newsfeed to collect items for play (Farmville). When I return to the newsfeed, I find that GET data. What exactly is this and is it affecting my computer and most importantly how do I get rid of it? Thank you.

Then they maybe in the source code of those feed items.

You can open the feed page in as tab and hover the links to see the link at the bottom of the page.

I see, thanks for your help.