Taken from this page at labnol.org
While you are on the web page, press Ctrl+Shift+J on Windows or Cmd+Opt+J on Mac to open the Console window inside Chrome Developer tools. Now enter the following commands to replace all occurrences of the word ABC with XYZ.
document.body.innerHTML = document.body.innerHTML.replace(/ABC/g, "XYZ")
document.head.innerHTML = document.head.innerHTML.replace(/ABC/g, "XYZ")