Question on Code in Mozilla's Array.prototype.indexOf
<p>This is Mozilla's Code in Mozilla's Array.prototype.indexOf</p>

<pre><code>if (!Array.prototype.indexOf)
{
  Array.prototype.indexOf = function(elt)
  {
    var len = this.length &gt;&gt;&gt; 0; // What does "&gt;&gt;&gt;" do?

    var from = Number(arguments[1]) || 0;
    from = (from &lt; 0) ? Math.ceil(from): Math.floor(from); 
    if (from &lt; 0)from += len;

    for (; from &lt; len; from++)
    {
      if (from in this &amp;&amp; this[from] === elt)return from;
    }
    return -1;
  };
}
</code></pre>

<p>I don't understand some of the syntax.<br />
What does ">>>" do in the above code?</p>
