CSS画三角

这个还是比较常用的

<div class="arrow-up"></div>
<div class="arrow-down"></div>
<div class="arrow-left"></div>
<div class="arrow-right"></div>

css如下：

.arrow-up {
 width: 0; 
 height: 0; 
 border-left: 5px solid transparent;
 border-right: 5px solid transparent;
 border-bottom: 5px solid black;
}

.arrow-down {
 width: 0; 
 height: 0; 
 border-left: 20px solid transparent;
 border-right: 20px solid transparent;
 border-top: 20px solid #f00;
}

.arrow-right {
 width: 0; 
 height: 0; 
 border-top: 60px solid transparent;
 border-bottom: 60px solid transparent;
 border-left: 60px solid green;
}

.arrow-left {
 width: 0; 
 height: 0; 
 border-top: 10px solid transparent;
 border-bottom: 10px solid transparent; 
 border-right:10px solid blue; 
}

可以在这 http://jsbin.com/wetosuqobo/edit?html,css,output 看下效果或者自己搞下