<html> <body> <style> .trlangle{ width: 0; height: 0; border-left: 50px solid transparent; border-right: 50px solid transparent; border-bottom: 100px solid red; } </style> <div class="trlangle"></div> </body> </html>
2.
<html> <body> <style> .triangle_border_up{ width:0; height:0; border-width:0 30px 30px; border-style:solid; border-color:transparent transparent #333;/*透明 透明 灰*/ margin:40px auto; position:relative; } .triangle_border_up span{ display:block; width:0; height:0; border-width:0 28px 28px; border-style:solid; border-color:transparent transparent #fc0;/*透明 透明 黄*/ position:absolute; top:0px; left:0px; } </style> <div class="triangle_border_up"> <span></span> </div> </body> </html>