...It's called Mozilla X-Ray Goggles, and it allows you to make a copy of an existing web page, edit its code, and change its appearance (including what it says). It doesn't actually hack the original page, of course -- it just makes this new re-mixed version of the page as you have re-created it.
And what a PERFECT week to find this tool! The news here in the US, on the major news networks was SO bad, SO sad... It was actually therapeutic to build an imaginary page of CNN, 50 years from now. CNN now stands for "Canine News Network" because finally we realize that dogs are the best, always. We -- humans -- needed a break from trying to lead this country.
Here's the link: