The incremental redesign of March 2014 introduced a new method for navigation and easier access to folders/recent among smaller improvements.

My enhancements:
- move the nav-bar to the top right next to username and settings to save vertical space.
- flatten the user-specific folders along with the normal folders
- remove the search web button
- bold the sender names in the message list to distinguish it more from the subject when message is already read
- make the folder area slimmer to allow for wider message reading

Known issues:
- will not support long usernames
- will not support long folder names
- lower left theme switcher button is not made thinner
- cannot create a new folder without disabling userstyle

Other useful styles:
- http://freestyler.ws/style/52307/yahoo-mail-remove-ads-better