Suggested layouts (only enable one at the time):
→ http://freestyler.ws/style/56847/wikipedia-layout-enhanced (comprehensive layout, http://imageshack.us/a/img545/3079/wiki03.png).
→ http://freestyler.ws/style/55738/wikipedia-clean-readable (minimal layout, removes stuff).

Works on most Wikimedia sites, such as wikipedia.org, wikimedia.org, wiktionary.org, wikiquote.org, wikibooks.org, wikisource.org, wikinews.org, wikiversity.org and mediawiki.org

Latest changes:
2014-09-27 - minor fixes.
2014-05-02 - https://en.wikipedia.org/wiki/Fitts's_law are now inverted to white text on dark background.
2014-01-02 - reverted yesterday's change.
2014-01-01 - tried to fix color pages on Wikipedia, as http://forum.userstyles.org/discussion/39633/bug-colour - if you see any bright backgrounds that shouldn't be there, please let me know. Happy New Year!
2013-11-13 - styled some popups and menus; fixed coordinates on mouseover; made places on maps black - if you consequently find black text somewhere where it shouldn't be, please let me know.
2013-09-19 - fixed the new "VisualEditor", again.
2013-08-05 - fixed the new "VisualEditor".
2013-07-07 - fixed the new language selection popup.
2013-06-17 - fixed some transparent images, like on https://en.wikipedia.org/wiki/Guitar (thanks for reporting)
2013-06-01 - tweaked backgrounds of logos.
2013-05-31 - added wikivoyage.org domain; added background behind logos, per request.
2013-05-14 - added URLs starting with "http://www.baka-tsuki.org/project/".