建一个文件夹，文件夹里面放两个文件，一个是login.html文件，存放html代码，一个是login.css文件,存放css代码
html
<!DOCTYPE html><html lang="en"><head><meta charset=UTF-8"><title>程序员之家</title><link rel="stylesheet" href="login.css"></head><body><div id="head"><ul><li><a>首页</a></li><li><a>博客</a></li><li><a>程序员学院</a></li><li><a>论坛</a></li><li><a>问答</a></li><li><a>代码</a></li><li><a>高校</a></li><li><a href="/" target="blank">CSDN</a></li><li><a href="/" target="blank">博客园</a></li><li><a>登录/注册</a></li><li><a>会员中心</a></li></ul></div><divstyle="background-image: url(download.jfif); background-size:100% 100%;margin-left: auto;margin-right: auto;width: 100%;height: 635px;"><section id="content"><div class="header"><a href="javascript:;" class="current">我要登录</a><a href="javascript:;">我要注册</a></div><div id=body><div class="dom" style="display: block;"><form><div id="s1"><h>账号</h><input id="input" type="text" placeholder="手机/邮箱/用户名"></div><div id="s1"><h>密码</h><input id="input" type="password" placeholder="密码"></div><div id="s1"><input type="checkbox"><span>记住密码</span></div><input id="button" type="submit" value="登 录"></form><div id="s1"><a href="#">找回密码</a><span>|</span><span>还没有注册帐号?</span><a href="#">立即注册</a></div><div id="s2"><span>使用第三方账号直接登录</span><div class="s3"><a href="#"><img src="images/qq.png" alt=""></a><a href="#"><img src="images/wechat.png" alt=""></a></div></div></div><div class="dom"><form><div id="s1"><h>手机号码</h><input id="input" type="text" placeholder="填写你的手机号码作为登录账户"></div><div id="s1"><h>用户名</h><input id="input" type="password" placeholder="中、英文均可, 最长20个字符或10个汉字"></div><div id="s1"><h>密码</h><input id="input" type="text" placeholder="6-30位英文、数字、符号, 区分大小写"></div><div id="s1"><h>短信验证码</h><br><input id="input1" type="text" placeholder="填写短信验证码"><input id="button1" type="button" value="获取短信验证码"></div><input id="button" type="submit" value="注 册"></form><div id="s2"><span>使用第三方账号直接登录</span><div class="s3"><a href="#"><img src="images/qq.png" alt=""></a><a href="#"><img src="images/wechat.png" alt=""></a></div></div></div></div></section><script>window.onload = function () {// 1.1 获取需要的标签let as = document.getElementsByClassName('header')[0].getElementsByTagName('a');let contents = document.getElementsByClassName('dom');// 1.2 遍历for (let i = 0; i < as.length; i++) {// 1.2.1 取出单个对象let a = as[i];a.id = i;// 1.2.2 监听鼠标的移动事件a.onclick = function () {// 让所有的a的class都清除for (let j = 0; j < as.length; j++) {as[j].className = '';contents[j].style.display = 'none';}// 设置当前a的classthis.className = 'current';// 从contents数组中取出对应的标签contents[this.id].style.display = 'block';}}}</script></div></div><div id="foot"><ul><li><a>关于我们</a></li><li><a>招贤纳士</a></li><li><a>广告服务</a></li><li><a>开发助手</a></li><li><a>工作时间 8:30-22:00</a></li></ul></div><div align="center" style="color: grey; font-size:12px;">Copyright © -. All Rights Reserved</div></body></html>
css
body,html,div {padding: 0;margin: 0;}#head {width: 100%;height: 43px;}#head ul {list-style-type: none;margin: 0;padding: 0;}#head ul li {float: left;}#head ul li a {display: block;width: 139.6px;color: black;background-color: white;text-align: center;text-decoration: none;margin: 0;padding-top: 10px;padding-bottom: 10px;font-size: 18px;}#head ul li a:hover {background-color: gray;}#foot {width: 100%;height: 42px;margin-top: 10px;}#foot ul {list-style-type: none;margin: 0;padding: 0;}#foot ul li {float: left;}#foot ul li a {display: block;width: 250px;color: grey;background-color: white;text-align: center;padding: 4px;text-decoration: none;line-height: 30px;font-size: 14px;}* {text-decoration: none;}a {color: blue;}input,button {outline: none;}#content {border: solid 2px #e0e0e0;width: 25rem;height: 33rem;background-color: white;margin-top: 50px;margin-left: 50%;float: left;}.header a {width: 50%;height: 60px;background-color: #f5f5f5;display: inline-block;float: left;/*居中*/text-align: center;line-height: 60px;color: #262626;}.header a.current {background-color: transparent;color: blue;}#body {margin: 2rem;}.dom {width: 100%;display: none;}#input {width: 100%;height: 2rem;margin-top: 0.5rem;padding-left: 0.5rem;border-radius: 5px;border: 1px solid #cccccc;}#s1 {margin-bottom: 1rem;}#button {width: 100%;height: 2rem;border: none;font-size: 1.5em;color: #fff;background-color: blueviolet;border-radius: 3px;margin-bottom: 1rem;}#s2 {text-align: center;}#s3 {margin-top: 1rem;}#input1 {width: 60%;height: 2rem;margin-top: 0.5rem;padding-left: 0.5rem;border-radius: 5px;border: 1px solid #cccccc;}#button1 {width: 35%;height: 2rem;margin-top: 0.5rem;padding-left: 0.5rem;border-radius: 5px;border: 1px solid #cccccc;cursor: pointer;}
