This is a Chrome extension that displays a banner when the URL of the current page matches a specified substring or regular expression.
I wrote this because, as a developer, I frequently switch between development and production environments and would like a visible warning before I publish "LOL BUTTS TESTING123" on the public website of my employer.
To specify a list of URLs to display the banner on and other settings, go to the Chrome Extensions page and click the Options link under the extension.
If you find a bug or want to contribute a new feature, submit a pull request!