1.Grouping
2.Nesting
If the CSS is structured well, there shouldn’t be a need to use many class or ID selectors.
【CSS】Intermediate2:Grouping and Nesting,布布扣,bubuko.com
【CSS】Intermediate2:Grouping and Nesting
原文：http://www.cnblogs.com/yzhen/p/3659377.html