What ever you just tried to do, the computer didn't like it.
Computers notorious for having no sense of humour, and very little ability to think laterally.
Of course now that I've said that my computer will never work for me again.
Leaving all that aside, you are a bit stuck aren't you? Try doing what every it was you
were trying to do again, and if all else fails please email email@example.com
to complain. LOUDLY. It would be really handy if you can send me the link
to the page that is misbehaving, and explain what you were trying to do.
Thanks, and sorry for the inconvenience.