From Fedora Project Wiki

Getting Started: The Stylesheets You Need, How They Work, and How to Use Them

The Fedora project's various web sites and web applications share, in at least some part, the very same stylesheets, icons, and other images in order to ensure a more consistent branding across fedoraproject.org, as well as to reduce the amount of redundant work our web developers need to do in order to put a site or application together.

Fedoracommunity fedora-css-hierarchy.png

In the diagram above, you can see that all three web sites, fedoraproject.org, Fedora Community, and Fedora Spins share the common Fedora web template defined by the fedora.css stylesheet: