用：before ：after 来写一些小特效

提起：before ：after首先想到的是 —— 用它来去浮动来我们来换个方式玩接下来展示三种用：before ：after来实现的特效 希望能起到抛砖引玉的作用

<一>第一种就是常见的小三角

直接上干货了：

//在你想要添加三角的地方加上 

.demo:after

{

content: "";

position: absolute;

top: 80%; left: 50%;

border-top: .6em solid #5BC0DE;

border-left: .6em solid transparent;

border-right: .6em solid transparent;

margin-left: -.6em;

}

<二>多色border-bottom

.blog-nav

{

font-size:2em;

 padding: 0 1em 0 1em;

position: relative;

}

.blog-nav:before

{

content: "";

height: .25em;

62.5%;

position: absolute;

left: 8%;

background: #b1cf37;

bottom: -.25em;

}

.blog-nav:after{

content: "";

height: .25em;

30%;

position: absolute;

left: 70%;

background: #f48123;

bottom: -.25em;

}

 <三>鼠标hover往两端扩展特效

底部横线在鼠标移到元素上从中间往两端出现

.title {

color:black;

font-weight: 500;

font-size: 2em;

transition: color .3s;

position: relative;

display: inline-block; }

.title:before{

height: 3px;

background-color:

#5BC0DE;

transform: scaleX(0) ;

content: "";

position: absolute; 100%;

bottom: 0; left: 0;

transition-duration: .2s;

transition-timing-function: ease-in-out;

transition-delay: 0s;

}

.title:hover:before

{

transform: scaleX(1);

content: "";

float:left;

100%;

bottom: 0;

left: 0;

transition-duration: .2s;

transition-timing-function: ease-in-out;

transition-delay: 0s;

}