我专门针对 nth-child(2n),但是具有给定类的兄弟姐妹的第一个、第三个等正在应用 css。
http://jsfiddle.net/relitnosmoge/9HCnH/1/
.grid > section.fifty:nth-child(2n) {
background: red !important;
margin-right: 0 !important;
margin-left: 0 !important;
}
<article class="block grid">
<section class="block hundred"></section>
<section class="block fifty"></section>
<section class="block fifty"></section>
<section class="block fifty"></section>
<section class="block fifty"></section>
</article>