If you are looking for a minimalistic Gmail skin, here's are the links:
- Stylesheet download: http://www.josefrichter.com/helvetimail.css
- Helvetimail home page: http://www.josefrichter.com/helvetimail/
- David's home page: http://tehdik.com
Requirements: The stylesheet only works with the latest Mailplane 2.1-beta version.
Installation: Assign the downloaded file to the Mailplane > Preferences > Tweak UI > Custom Stylesheet setting.
Important: Gmail is changing all the time! If the stylesheet stops working, please check the Helvetimail or David's page for a new version.
Tip: As an alternative take a look at Gmail's built-in Themes. They are maintained by Google and will keep up with Gmail's changes.
Thanks David Klein for sharing!