title: Red textbox border color
body: <p>I have a form with one textbox. I want to check when the textbox value is empty and make some sort of red border surrounding the textbox itself when it's empty.</p>
  
  <pre><code>if (document.getElementById('pageh').value == "") {
      alert("One of the fields is empty.");
      return false;
  }
  </code></pre>
  
  <p>That's my validation, but how do I add the red border?</p>