CSS绘制对话框三角形

.dialog {
    width: 200px;
    height: 135px;
    background: #888;
    border-radius: 24px;
    position: relative;
    top: 30px;
    padding: 8px 6px;
    z-index: 0;
    font-size: 11px;
    line-height: 1.5;
}
.dialog:after {
    content: "";
    position: absolute;
    bottom: 41px;
    right: -34px;
    width: 0;
    height: 0;
    border-bottom: 60px solid #888;
    border-right: 80px solid transparent;
    transform: rotate(25deg);
    z-index: -1;
}

参考链接：CSS绘制三角形和箭头