8fold Web Assets
8fold Web Assets is an extension and derivation of the US Web Design system being developed and maintained by the fine folks over at 18F (and the broader community) as an effort to improve the quality of websites produced by the Federal Government. They are working very hard to define accessible HTML patterns and an elegant style. It is definitely a project we watch and contribute to whenever possible.
If you have questions regarding a component, you can probably go to the US Web Design system and learn more about it.