When you're developping Web applications, you often ask yourself what does your beautiful design will look like if your users enter a very long text. Or you may want to prototype a new screen based on an existing one, I came around a quick hack using HTML5 goodness: content editable !

On the page you want to edit, open your JavaScript console (Cmd+Alt+I on Chrome Mac), and enter the following

  document.body.contentEditable = true;