纯CSS实现tooltip提示框，CSS箭头及形状之续篇--给整个tooltip提示框加个边框

学习了：https://blog.csdn.net/u012688910/article/details/41856895

 源码膜拜：

 

.demo{
                   background-color: gray;                height: 100px;                position: relative;                width: 100px;            border:2.75px solid red;            }        .demo:after,.demo:before{
               content:'';            position:absolute;        }        .demo:after{
               //height:20px;            //width:20px;            //background:yellow;            //border:10px  solid lightgreen;            border:10px  solid transparent;            border-top-color:gray;            top:100px;            left:20px;        }                    .demo:before{
               //height:30px;            //width:30px;            //background:green;            //border:15px solid red;            border:15px solid transparent;            border-top-color:red;            top:100px;            left:15px;        }