一、正常情况效果
二、某项没有填写的效果
三、没有勾选同意项的效果
四、代码
<!DOCTYPE html>
<html>
<head><meta charset="UTF-8"><title>注册</title><style>body {font-family: Arial, sans-serif;background-color: #f5f5f5;}form {max-width: 500px;margin: 50px auto;padding: 40px;background-color: #fff;box-shadow: 0 2px 4px rgba(0,0,0,0.2);border-radius: 6px;}h1 {font-size: 36px;text-align: center;margin-top: 0;color: #2c3e50;text-shadow: 1px 1px 0 #fff;}label {display: block;margin-bottom: 10px;color: #2c3e50;text-shadow: 1px 1px 0 #fff;font-size: 18px;}input {padding: 10px;width: 100%;border: 1px solid #ccc;border-radius: 4px;margin-bottom: 20px;box-sizing: border-box;font-size: 16px;color: #2c3e50;}input:focus {outline: none;border-color: #51a6ff;}input[type="checkbox"] {width: auto;margin-top: 10px;margin-right: 5px;}button[type="submit"] {padding: 12px 24px;background-color: #51a6ff;color: #fff;border: none;border-radius: 4px;cursor: pointer;transition: all 0.3s ease;font-size: 20px;}button[type="submit"]:hover {background-color: #0072c6;}.error {color: #ff4d4d;font-size: 14px;margin-top: 5px;}</style>
</head>
<body><form><h1>注册</h1><label>用户名：</label><input type="text" name="username" required><label>密码：</label><input type="password" name="password" required><label>确认密码：</label><input type="password" name="confirm_password" required><label><input type="checkbox" name="agree" required>我已同意<a href="#">注册协议</a></label><p style="text-align: right;"><button type="submit">注册</button></p></form>
</body>
</html>
