There are plenty of complaints about this on discussions.apple.com. It seems to only happen with iPads running the more popular browsers. I tried it with Puffin and everything was fine. Oddly enough, if you tap on the link the video loads anyway despite the error message.
Facebook for iPad sucks. And not just by a bit, it's a horrible, horrible app that's needs to be destroyed or thrown into the everlasting lake of fire. -- If you can't explain it simply, you don't understand it well enough. - Albert Einstein