Sorry about the issue with the course! I tested out the challenge on your account and it seems to work okay with the provided solution.
Actually, I tested out your solution that's posted above and that works okay to complete the 3rd objective.
My guess is that it might be a browser plugin or extension that's breaking the challenge. It looks like you're running Firefox 39 on OS X, which should be fine. But if you're running Adblock or HTTPSEverywhere or an extension that might be causing issues then disabling it might work. Or a switch to a different browser helps sometimes too:
I tested on Firefox 39.0 and it seems to work okay there too:
Sorry about the frustration! Thanks for letting us know, though, because this sparked a discussion here on our end about trying to start detecting extensions to see if the courses can start giving better feedback about it.
Let me know if there's anything else I can do to follow up and help out!