Need some explanation on HTML, nth-child

Question

NOTE: SEE BELOW FOR CLEARER EXPLANATION

I\'m trying to figure out why this is happening.

jsFiddle 1 - Before

HTML

Answer 1

use these

.big-chix:nth-child(even) { background-color:#eee; }
.big-chix:nth-child(odd) { background-color:#aaa; }

works in http://jsfiddle.net/TeqUF/2/