From Fedora Project Wiki
(inserting note for integration into other text)
- There have been many changes to theming in GTK+ 3, where a stable API has not been declared. As a result, applications that use custom CSS theming, for example, may show issues with their appearance. This may include default applications that come with Fedora 24 Alpha Workstation. Users are asked to try out their favorite GTK+ 3 based applications and report bugs upstream so they might be addressed in time for the final release.