border-left:100px solid transparent; 左边框隐藏
transform:rotate(45deg); div旋转45度
用css做一个三角形
<style type="text/css"> #a{ width:0px; height:0px; border-top:100px solid #00C; border-left:100px solid transparent; border-right:100px solid transparent;} </style> <body> <div id="a"></div> </body>