The Hacker News post about creating a one line browser notepad reminded me of a neat trick one of my friends showed me. Try loading this html into Chrome (or any browser that supports contenteditable="plaintext-only").

  <head style="display: block">
    <style style="display: block"
      body {
        background-color: #ccc;
    <h1>My style really shows...</h1>

You should immediately notice the style element is now visible. Moreover you can edit it and see the changes reflected on the page. Because content-editable is set to plaintext-only, you can even add new lines to the style without pesky paragraph tags getting inserted and breaking everything.