title: Javascript not-well formed error in for loop
body: <p>I copied this code from an <a href="http://www.lazycoder.com/weblog/2009/08/12/a-simple-map-function-for-plain-javascript-arrays/" rel="noreferrer">example</a>. I've read it 100 times.</p>
  
  <pre><code>Array.prototype.map = function(fn) {
      var r = [];
      var l = this.length;
      for(var i = 0; i &lt; l; i++) {
          r.push(fn(this[i]));
      }
      return r;
  };
  </code></pre>
  
  <p>Why does Firefox say:</p>
  
  <pre><code>not well-formed
  file:///some/path.html                         Line: 5
      for(var i = 0; i &lt; l; i++) {
      -------------------^
  </code></pre>
  
  <p><strong>UPDATE</strong></p>
  
  <p>The error is only shown when Firebug is turned on for the page.</p>