区块上的三角形状的css写法

.navbar .navline > .dropdown > .dropdown-menu:before {
    content: '';
    display: inline-block;
    border-left: 7px solid transparent;
    border-right: 7px solid transparent;
    border-bottom: 7px solid #ccc;
    border-bottom-color: rgba(0,0,0,0.2);
    position: absolute;
    top: -7px;
    left: 59px;
}

.navbar .navline > .dropdown > .dropdown-menu:after {
    content: '';
    display: inline-block;
    border-left: 6px solid transparent;
    border-right: 6px solid transparent;
    border-bottom: 6px solid #ffffff;
    position: absolute;
    top: -6px;
    left: 60px;
}