When I say "taking over my clipboard" I mean it appears on my clipboard and can't be removed. Whenever I paste, that's what gets pasted. If I copy something else and then paste, whatever I copied isn't actually copied and that string is what gets pasted. I even went and searched the system files for the actual file where the clipboard stores things and couldn't figure out how to remove it from there (though I didn't try just deleting it, just in case it would mess with the system).
And yeah, I checked out the site after it started doing that to see who was doing that and if there was any way to track them, report them, whatever, and it was pretty obviously a crock. I didn't click on anything on that page, and I didn't visit it until after it had taken over my clipboard (actually, the first time I visited was because I copied a word to search for and pasted it into the firefox address bar, because it usually just takes you to a Wikipedia search for that word, and wound up at the site because I was too hasty in hitting the return key after pasting to make sure it had pasted properly). And actually, on this computer (the 2nd one), I haven't visited that site at all.
I do know there are ways to make pages copy things to clipboards (normally I've seen them used where you clicked a button before it copied), but I've never seen an instance where it would then prevent you from copying anything else.