关于CSS伪类选择器_html/css_WEB-ITnose
#CSS伪类选择器
##使用css伪类选择器需要注意的
使用css的伪类选择器来选择某元素时，需要特别注意```:first-child```和```:nth-child(n)```等时，
网页渲染是从语句的后面开始读取的，也就是说，类似```p:first-child```这样的伪类选择器，指的是“某元素的以p元素作为第一子项的那项”，而不是“p元素的第一个子项”，原因是因为，其实这里在p：之前，省略了xxx & nbsp;这几个字符，导致很容易产生误解。
e.g.
div p:first-child{color:red;}
111
222
333
这里的222字符不会变红，因为它不是div元素的以p元素为第一子项的那个元素，在这个例子中，div 元素以p元素作为第一子项是不成立的，没有任何一个元素符合这个条件，h1元素也不会响应color:red.
##用css伪类选择器去除带有边框的最后一个元素的办法
如果在设计一个导航栏时，每个元素之间有竖线相隔，通过伪类选择器可以很简洁地去除最后一个li元素的右边框线。
li{
border-right:1px red solid;
}
ul li:last-child{
border-right:none;
}
即可去除最右边的也就是最后一个li的有边框线，而不用额外给最后一个li取名。
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