However this operation doesn't remove whitespace-only Text nodes, because they're not empty — they contain whitespace, and although whitespace is usually insignificant, an implementation should not presume that.

Therefore even a normalized node may have a different subtree between browsers — for example, Firefox counts whitespace-only text nodes as part of the DOM, whereas Internet Explorer ignores them. To gain a truly uniform DOM you can use a whitespace stripping method, such as this one by Alex Vincent:

function cleanWhitespace(node)
{
  for (var i=0; i<node.childNodes.length; i++)
  {
    var child = node.childNodes[i];
    if(child.nodeType == 3 && !/\S/.test(child.nodeValue))
    {
      node.removeChild(child);
      i--;
    }
    if(child.nodeType == 1)
    {
      cleanWhitespace(child);
    }
  }
  return node;
}

The example above will remove all text nodes that only contain whitespace, making the sub-tree underneath node consistent between browsers, and can be called like this:

cleanWhitespace(node);

So if we started with this HTML:

<blockquote class="yoda">
  <p>
    When nine-hundred years old you reach,
    look as good you will not!
  </p>
</blockquote>

Running cleanWhitespace on the <blockquote> element would produce this result:

<blockquote class="yoda"><p>When nine-hundred years old you reach, look as good you will not!</p></blockquote>