title: `onsubmit` of html form doesn't work
body: <p>The html code is simple:</p>
  
  <pre><code>&lt;form onsubmit="submitAdvice(this);return false;"&gt;
      &lt;input type="submit" value="submit" /&gt;
  &lt;/form&gt;​
  </code></pre>
  
  <p>And the javascript code:</p>
  
  <pre><code>function submitAdvice(f) {
      alert('submitting');
  }
  </code></pre>
  
  <p>But when I click the <code>submit</code> button, it doesn't alert <code>submitting</code>, instead, it submits the form.</p>
  
  <p>I don't know where is wrong.</p>
  
  <p>PS: the live demo: <a href="http://jsfiddle.net/yc6cq/" rel="nofollow noreferrer">http://jsfiddle.net/yc6cq/</a></p>
  
  <hr>
  
  <p>I just found the reason, it caused by jsfiddle!</p>
  
  <p><img src="https://i.stack.imgur.com/ZPFC5.jpg" alt="enter image description here"></p>
  
  <p>Please note it will load <code>mootools 1.4.5</code> on <code>onLoad</code> event. Everything will be OK if I set it as <code>no wrap</code></p>