admin.html

<html>

<head>
    <title>Admin Login</title>
    <link href="style.css" rel="stylesheet">
    <script>
        function validate_form()
        {

            var usr= document.getElementById('usr-name').value;
            var pass= document.getElementById('passwd').value;
            
            if(usr=="")
            { document.getElementById('error-container').innerHTML= "User name can't be empty";
                return false;
            }

            if(pass=="")
            {     document.getElementById('error-container').innerHTML= "Password can't be empty";
                  return false;
            }


        }
    </script>
</head>

<body>

<div class="page-container">
    <div class="form-container" id="container-1">
        <h2>Sign In</h2>
        <span class="error-container" id="error-container"></span>
        <form action="AdminServlet" method="post">
            <label>Username:</label><br>
            <input type="text" name="Username" id="usr-name"><br><br>
            <label>Password:</label><br>
            <input type="text" name="Password" id="passwd"><br><br>

            <button onclick="return validate_form();" class="btn" type="submit" id="login">LOGIN</button>

        </form>

    </div>
</div>
    
</body>

</html>