Augment UI design contrast with 3rd party sites.

The keybase.io popups are very visually similar in UI to twitter's and facebook's and linkedin's and many others. I'm wont claim that this is a huge issue in the long run, but having a more distinctive look and feel would help beginners. When setting up my Twitter proof via the browser flow I got slightly confused and thought the last box was actually a tweet box. I - a human - can be dumb and lazy that way sometimes.

The issue identifies keybase.io popups and the Twitter proof browser flow, but names no files, tests, or entry points. First locate the popup UI and browser-flow entry point, then define a distinctive visual treatment and a clear way to verify that beginners no longer confuse the final box with a tweet box.

Written by the indexing model from the issue text.