css selectors - What is the alternative to CSS-selecting an ancestor

CSS(3) has descendent selectors, e.g. td em {color: red};, but no ancestor selector, apparently.

So, what should I do instead of something like td {border: 1pt solid red} em; ? i.e., how can I set a style on ancestors of some (X)HTML element?

Note:

• Javascript is not relevant for the workaround, something XPath'y might be.

Answer

You can wait for CSS4 selectors to be implemented, then do

td! em {
    border: 1pt solid red;
}

See http://dev.w3.org/csswg/selectors4/.

Or...

var xpathresult = document.evaluate("//td[.//em]", 
    document, null, XPathResult.ANY_TYPE, null); 
while (e=xpathresult.iterateNext()){
    e.classList.add("border");
}

See https://developer.mozilla.org/en-US/docs/DOM/document.evaluate. Normal browser support caveats apply.