@namespace url(http://www.w3.org/1999/xhtml);

@-moz-document url-prefix("http://cms.blog.livedoor.com/cms/article/preview"),
               url-prefix("http://cms.blog.livedoor.com/cms/design/preview") {
  iframe[name="preview_inner"] {
    width: 100% !important;
  }
}