<div class="container">
  <form action="/action_page.php">
    <label for="usrname">Username</label>
    <input type="text" id="usrname" name="usrname" required>

    <label for="psw">Password</label>
  <  input type="password" id="psw" name="psw" pattern="(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,}" title="Must contain at least one number and one uppercase and lowercase letter, and at least 8 or more characters" required>

    <input type="submit" value="Submit">
  </form>
</div>

<div id="message">
  <h3>Password must contain the following:</h3>
  <p id="letter" class="invalid">A <b>lowercase</b> letter</p>
  <p id="capital" class="invalid">A <b>capital (uppercase)</b> letter</p>
  <p id="number" class="invalid">A <b>number</b></p>
  <p id="length" class="invalid">Minimum <b>8 characters</b></p>
</div>

/* Style all input fields */
input {
  width: 100%;
  padding: 12px;
  border: 1px solid #ccc;
  border-radius: 4px;
  box-sizing: border-box;
  margin-top: 6px;
  margin-bottom: 16px;
}

/* Style the submit button */
input[type=submit] {
  background-color: #04AA6D;
  color: white;
}

/* Style the container for inputs */
.container {
  background-color: #f1f1f1;
  padding: 20px;
}

/* The message box is shown when the user clicks on the password field */
#message {
  display:none;
  background: #f1f1f1;
  color: #000;
  position: relative;
  padding: 20px;
  margin-top: 10px;
}

#message p {
  padding: 10px 35px;
  font-size: 18px;
}

/* Add a green text color and a checkmark when the requirements are right */
.valid {
  color: green;
}

.valid:before {
  position: relative;
  left: -35px;
  content: "&#10004;";
}

/* Add a red text color and an "x" icon when the requirements are wrong */
.invalid {
  color: red;
}

.invalid:before {
  position: relative;
  left: -35px;
  content: "&#10006;";
}