效果
HTML：
<!doctype html> <html lang="en"> <head> <meta charset="utf-8"> <title>CSS Triangle Demo</title> <link rel="stylesheet" href="triangle.css"> </head>
<body> <h3>Down Triangle</h3> <div class="down-triangle"> </div> <h3>Up Triangle</h3> <div class="up-triangle"> </div> <h3>Left Triangle</h3> <div class="left-triangle"> </div> <h3>Right Triangle</h3> <div class="right-triangle"> </div> </body> </html>
CSS：（triangle.css）
.down-triangle { width: 0; height: 0; border-width: 10px 10px 0 10px; border-style: solid; border-color: #dc291e transparent; } .up-triangle { width: 0; height: 0; border-width: 0px 10px 10px 10px; border-style: solid; border-color: #dc291e transparent; } .left-triangle { width: 0; height: 0; border-width: 10px 10px 10px 0px; border-style: solid; border-color: transparent #dc291e; } .right-triangle { width: 0; height: 0; border-width: 10px 0px 10px 10px; border-style: solid; border-color: transparent #dc291e; }
github链接：中