用css写个三角形

样例：

代码：

html:


<div class="tips">
<span class="caret"></span>
我是一个tooltip
</div>

css:


.tips {width: 200px;height: 50px;line-height: 50px;text-align: center;position: relative;margin: 20px auto;border: 1px solid orange;border-radius: 3px;
}
.tips .caret {top: -10px;left: 10px;position: absolute;width: 10px;height: 10px;
}
.tips .caret:before, .tips .caret:after {content: "";position: absolute;
}
.tips .caret:before {top: 0;left: 0;border-bottom: 10px solid orange;border-left: 10px solid transparent;border-right: 10px solid transparent;
}
.tips .caret:after {left: 1px;top: 1px;border-bottom: 9px solid #fff;border-left: 9px solid transparent;border-right: 9px solid transparent;
}

实现原理：使用border和伪类:after、:before来实现

解析：

border-left; border-right; border-top; border-bottom; 的作用范围

=========================================


<html>
<head><style type="text/css">.tips {width: 0;height: 0; border-left: 100px solid orange;border-right: 100px solid red;border-top: 100px solid green;border-bottom: 100px solid blue;}</style>
</head><body><div class="tips"></div></body>
</html>

=====================================

效果：

把border-left, border-right, border-top 设为透明，


.tips3{border-left: 100px solid transparent;border-right: 100px solid transparent;border-top: 100px solid transparent;border-bottom: 100px solid blue;
}

则剩下：