This extension activates or deactivates the built-in dark theme of twitter.com. Also it provides a few customization on how the dark theme applies. For instance you can convert the global text color or background color.
Note that since this theme is written on top of the built-in theme, it is more stable compared to the user-styles that are installed using Stylish or Stylus add-ons.
If you have ideas on how to improve this theme please add a note on the review section of http://add0n.com/dark-theme.html?from=twitter