css实现下箭头

<div class="top"></div>

css实现上箭头

.top {

    width:;

    height:;

    border-left: 10px solid transparent;

    border-right: 10px solid transparent;

    border-bottom: 10px solid #217AFF;

}

css实现下箭头

.top {

    width:;

    height:;

    border-left: 10px solid transparent;

    border-right: 10px solid transparent;

    border-top: 10px solid #217AFF;

}