[2] Mozilla Firefox 0.7 についてる UA スタイルシートにはこんな記述があります:
/* Quirk: Make sure that the residual style tags' size info.
* does not take precedence over heading tags' size. (b=77352)
* Note: This special attribute is set only for a residual
* style tag within a heading tag.
*/
/* XXX This is a potential performance problem. This should not be
* using an attribute!
*/
*[_moz-rs-heading] {
font-size: inherit !important;
}(名無しさん [sage])
[3] <http://software.hixie.ch/utilities/js/live-dom-viewer/?%3Ci%3E%3Ch1%3Ea>