Modern CSS framework based on Flexbox

Mozilla's new typeface, used in Firefox OS

Simpsons characters in CSS

Friendlier HTML form controls with a little CSS magic.

Patterns for using flexbox CSS to build awesome UI components.

Arc Firefox Theme

📚 Dark theme for Stack Overflow & most Stack Exchange network sites

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An Utility CSS only library. It supports css grid and many more useful css properties.

Source code of reactphp.org.