PHP注册系统 - 错误的密码错误css

Question

当有人输入错误的用户名或密码时，我想突出显示红色的登录框，但它给了我一个失败的方面。

我想要的：

我是怎么做的：

HTML

    <div class="login">
<form action="" method="post" name="login">
<input type="text" name="username" placeholder="Username" required />
<input type="password" name="password" placeholder="Password" required />
<input type="image" src="https://i.imgur.com/uVoJ8Kl.pngg" />
</form>
</div>

PHP

<?php

 require('config.php');
 session_start();
 // If form submitted, insert values into the database.
 if (isset($_POST['password'])){
 $username = $_POST['username'];
 $password = $_POST['password'];
 $username = stripslashes($username);
 $username = mysql_real_escape_string($username);
 $password = stripslashes($password);
 $password = mysql_real_escape_string($password);
 //Checking is user existing in the database or not
 $query = "SELECT * FROM `users` WHERE username='$username' and password='".sha1($password)."'";
 $result = mysql_query($query) or die(mysql_error());
 $rows = mysql_num_rows($result);
 if($rows==1){
 $_SESSION['username'] = $username;
 header("Location: profile.php"); // Redirect user to index.php
 }else{
 echo "<div class='form'><h3>Username sau parola gresita. Click</h3><br/>Click  <a href='login.php'>aici</a> pentru a reveni la pagina de login</div>";
 }
 }else{
 }
?>

你能给我一个如何解决的提示吗？