伪类和伪元素选择器

.link:hover{
    color: yellow;
    font-weight: bold;
    /*倾斜*/
    font-style: italic;
}
/*before和after加的东西不能被选中*/
.box1:before{
    content: ".";
    color: red;
}
.box2:after{
    content: "。";
    color: blue;
}