核心提示：//html页面：p class=demo/pcss代码：body {background-color: #fff;}.demo {position: relative;width: 0;height...
//html页面：
<p class="demo"></p>
css代码：
body {
background-color: #fff;
}
.demo {
position: relative;
width: 0;
height: 0;
border-style: solid;
border-width: 0 10px 20px 10px;
border-color: transparent transparent #999 transparent;
}
.demo::before {
position: absolute;
content: '';
top: 1px;
left: -9.5px;
width: 0;
height: 0;
border-style: solid;
border-width: 0 9.5px 19px 9.5px;
border-color: transparent transparent #ffffff transparent;
}
 
