ここでは、HTML、CSS、JavaScriptを使用したシンプルな登録フォームとフォームバリデーションの例を示します：

HTML:

```php
<form id="signup-form">
  <div>
    <label for="first-name">First Name:</label>
    <input type="text" id="first-name" name="first-name" required>
  </div>
  <div>
    <label for="last-name">Last Name:</label>
    <input type="text" id="last-name" name="last-name" required>
  </div>
  <div>
    <label for="email">Email:</label>
    <input type="email" id="email" name="email" required>
  </div>
  <div>
    <label for="phone">Phone Number:</label>
    <input type="tel" id="phone" name="phone" required>
  </div>
  <div>
    <label for="password">Password:</label>
    <input type="password" id="password" name="password" required>
  </div>
  <div>
    <label for="password-confirm">Confirm Password:</label>
    <input type="password" id="password-confirm" name="password-confirm" required>
  </div>
  <button type="submit">Sign Up</button>
</form>
```

CSS:
```css
#signup-form {
  padding: 20px;
  background-color: #f2f2f2;
  width: 500px;
  margin: auto;
}

#signup-form label {
  display: block;
  margin-bottom: 10px;
  font-weight: bold;
}

#signup-form input[type="text"],
#signup-form input[type="email"],
#signup-form input[type="tel"],
#signup-form input[type="password"] {
  width: 100%;
  padding: 10px;
  margin-bottom: 20px;
  box-sizing: border-box;
  border: 1px solid #ccc;
  border-radius: 5px;
}
```

CSS:
```css
#signup-form button[type="submit"] {
  width: 100%;
  padding: 10px;
  background-color: #4CAF50;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#signup-form button[type="submit"]:hover {
  background-color: #3e8e41;
}
```

JavaScript:

```javascript
const form = document.querySelector("#signup-form");
const passwordInput = document.querySelector("#password");
const passwordConfirmInput = document.querySelector("#password-confirm");

form.addEventListener("submit", (event) => {
  event.preventDefault();

  if (passwordInput.value !== passwordConfirmInput.value) {
    alert("Password and password confirmation do not match.");
    return;
  }

  alert("Form submitted successfully!");
});
```
Here is an example of a simple sign up form using HTML, CSS, and JavaScript with form validation:

HTML:

'''php
<form id="signup-form">
  <div>
    <label for="first-name">First Name:</label>
    <input type="text" id="first-name" name="first-name" required>
  </div>
  <div>
    <label for="last-name">Last Name:</label>
    <input type="text" id="last-name" name="last-name" required>
  </div>
  <div>
    <label for="email">Email:</label>
    <input type="email" id="email" name="email" required>
  </div>
  <div>
    <label for="phone">Phone Number:</label>
    <input type="tel" id="phone" name="phone" required>
  </div>
  <div>
    <label for="password">Password:</label>
    <input type="password" id="password" name="password" required>
  </div>
  <div>
    <label for="password-confirm">Confirm Password:</label>
    <input type="password" id="password-confirm" name="password-confirm" required>
  </div>
  <button type="submit">Sign Up</button>
</form>
'''

CSS:
'''css
#signup-form {
  padding: 20px;
  background-color: #f2f2f2;
  width: 500px;
  margin: auto;
}

#signup-form label {
  display: block;
  margin-bottom: 10px;
  font-weight: bold;
}

#signup-form input[type="text"],
#signup-form input[type="email"],
#signup-form input[type="tel"],
#signup-form input[type="password"] {
  width: 100%;
  padding: 10px;
  margin-bottom: 20px;
  box-sizing: border-box;
  border: 1px solid #ccc;
  border-radius: 5px;
}

CSS:

#signup-form button[type="submit"] {
  width: 100%;
  padding: 10px;
  background-color: #4CAF50;
  color: white;
  border: none;
  border-radius: 5px;
  cursor: pointer;
}

#signup-form button[type="submit"]:hover {
  background-color: #3e8e41;
}
'''

JavaScript:

'''javascript
const form = document.querySelector("#signup-form");
const passwordInput = document.querySelector("#password");
const passwordConfirmInput = document.querySelector("#password-confirm");

form.addEventListener("submit", (event) => {
  event.preventDefault();

  if (passwordInput.value !== passwordConfirmInput.value) {
    alert("Password and password confirmation do not match.");
    return;
  }

  alert("Form submitted successfully!");
});
'''