常用的两种伪类选择器

一、结构伪类选择器

<style>
.catelist{
  margin: 20px;
}
/* 结构伪类选择器 */
.item:nth-of-type(2){
  color: red;
}
.item:nth-of-type(2n){
  background-color: rgb(227, 227, 227);
}
.item:nth-last-of-type(1){
  color: blue;
}
.item:nth-last-of-type(3){
  color: rgb(15, 241, 15);
}
</style>
<ol class="catelist">
  <li class="item">item1</li>
  <li class="item">item2</li>
  <li class="item">item3</li>
  <li class="item">item4</li>
  <li class="item">item5</li>
  <li class="item">item6</li>
  <li class="item">item7</li>
  <li class="item">item8</li>
</ol>

二、状态伪类选择器

<style>
/* 状态伪类选择器 */
input:focus{
    background-color: aquamarine;
    border: 1px dashed gray;
}
input:disabled{
  color: red;
  border: none;
}
button{
    width: 150px;
    height: 30px;
    border: none;
    margin-bottom: 10px;
    background-color: greenyellow;
}
button:hover{
    background-color: red;
    cursor: pointer;
    color: #fff;;
}
</style>
<div class="regist">
  <form action="check.php" method="post">
    <fieldset>
      <legend>用户注册</legend>
      <label>用户名：<input type="text" /></label>
      <label>
        性别：<input type="radio" name="sex" value="1" checked />男
        <input type="radio" name="sex" value="0" />女
      </label>
      <label>
        警告：<input type="text" value="一旦注册不可修改" disabled />
      </label>
      <button>提 交</button>
    </fieldset>
  </form>
</div>