title: Is call to preventDefault() really necessary on drop event?
body: <p>I am learning about Drag &amp; Drop. I have copied a W3Schools example in <a href="http://jsfiddle.net/3vKTS/1/" rel="noreferrer">JSFiddle</a>.</p>
  
  <p>The W3School example calls <code>preventDefault()</code> in the drop event:</p>
  
  <pre><code>function drop(ev) {
      ev.preventDefault();
      var data=ev.dataTransfer.getData("Text");
      ev.target.appendChild(document.getElementById(data));
  }
  </code></pre>
  
  <p>Yet, I don't understand the need when reading documentation. When I <a href="http://jsfiddle.net/3vKTS/3/" rel="noreferrer">remove this call</a>, the example still works fine:</p>
  
  <pre><code>function drop(ev) {
      var data=ev.dataTransfer.getData("Text");
      ev.target.appendChild(document.getElementById(data));
  }
  </code></pre>
  
  <p>So, what is the use of this call to <code>preventDefault()</code>? Do I really need it? If yes why?</p>