<div class="top"></div>
css实现上箭头
.top { width: 0; height: 0; border-left: 10px solid transparent; border-right: 10px solid transparent; border-bottom: 10px solid #217AFF; }
css实现下箭头
.top { width: 0; height: 0; border-left: 10px solid transparent; border-right: 10px solid transparent; border-top: 10px solid #217AFF; }