Style Formatter organizes your html and css and formats it so you can paste it into an existing page without the css getting overwritten.
Additionally, Style Formatter can be used to clean up and format existing html and css.
The example below is a straight copy of Google's 1998 homepage with a red background added. After formatting, any or all of the html and css can be easily edited and pasted into an existing site with its own styles and still look the same.
Like the navigation bar a site uses? You could use this to quickly isolate the element and play with it.