<svg xmlns="http://www.w3.org/2000/svg" width="300" height="200">
 <rect x="0" y="0" width="300" height="200" fill="green"/>
 <!-- This next line should be hidden since it has an unsupported
      value for the "width" attribute (it has a leading space, which
      isn't allowed by any prose in the spec as far as I can tell. -->
 <rect x="0" y="0" width=" 300" height="200" fill="red"/>
</svg>