<tal:block define="
  y_width options/youtube_width | nothing; 
  y_height options/youtube_height | nothing; 
  y_url options/youtube_url | nothing;
  ">
  <object type="application/x-shockwave-flash" data="" 
    tal:attributes="height y_height; width y_width; data y_url;">
    <param name="movie" value=""
      tal:attributes="value y_url;" />
    <param name="wmode" value="transparent" />
  </object>
</tal:block>
