Hi Team,

We are missing UA style sheet rule in our mathml.css:

Web-Spec: https://w3c.github.io/mathml-core/#error-message-merror

merror {
  border: 1px solid red;
  background-color: lightYellow;
}

and it leads to two progressions in WPT.

WPT Test Link: http://wpt.live/mathml/relations/css-styling/padding-border-margin/border-002.html

> Border properties on merror	
> Border properties on merror (rtl)	

____

Just wanted to raise so we can fix it.

Thanks!