This counter simply counts characters in given textarea (or wherever). It’s very simple and it doesn’t require any stupid huge JS library, it’s just plain JS.

window.onload = function () {
  var element = document.getElementById("twitter");
  var showDiv = document.getElementById("counter");
  var button  = document.getElementById("submit-button");
  var counter = new TwitterCounter(element, showDiv);
  counter.update();
  element.onkeyup = function () {
    counter.update();
    button.disabled = counter.lengthExceeded();
  };
};

<p>
  Remaining characters: <span id='counter'></span>
</p>
<form action="#" method="post">
  <div>
    <textarea id='twitter'>I'm the default text.</textarea>
  </div>
  <button id="submit-button" type="submit">Send!</button>
</form>

Do whatever you want with the code, but with NO warranty!