CSSで三角形を作成、ドロップダウンボックス三角_html/css_WEB-ITnose

    div {        width:0px;        height:0px;        border-top:20px solid transparent;        border-left:20px solid transparent;        border-right:20px solid transparent;        border-bottom:20px solid green;       }

<div></div>

div {    width:150px;    height:150px;    position:relative;    margin:50px auto;}div p {    border:1px solid #000;    width:100px;    height:100px;}div span {    display:block;    width:0px;    height:0px;    border-top:20px solid transparent;    border-left:20px solid transparent;    border-right:20px solid transparent;    border-bottom:20px solid black;    position:absolute;    top:-40px;    left:0;}div span.blank {    border-top:19px solid transparent;    border-left:19px solid transparent;    border-right:19px solid transparent;    border-bottom:19px solid white;    top:-37px;    left:1px;}