Полезное
References
When Can I Use
HTML5 Please
Instant Documentation Search
CSS Reference – MDN
Safari CSS Reference
The CSS3 Test
CSS Tools
Styleneat – CSS Organizer
ProCSSor – Advanced CSS Prettifier
CSSComb – Инструмент для сортировки CSS-свойств в нужном порядке
CSS with vertical rhythm
Ultimate CSS Gradient Generator
Em Calculator
ModularGrid
Modular Grid Pattern
Grid Calculator