> Again, what I care about is not the syntax but the functionality.
Issue here is that you're talking about this using syntax for something which has absolutely no relation. Which is a tad confusing.
No, what you want does not work in CSS, you can't make a selector conditional on a second completely unrelated selector (you probably can in XPath, although I'm sure your colleagues will soon look to end your life if you do)
Could you explain why? Let's say you have a clickable element and want to display a status text on hover. The status texts are loaded in some divs somewhere else on the page. You would need JS to catch onhover and then swap the display:hidden to block or whatever. Why would anybody look to "end my life" if that was possible?
div.status > span:on(div.clickme > a:hover) { display:block; }
Why would that be bad?
> Why would that be bad?
It's "action at a distance", it's very, very hard to understand and debug what happens.
body > div:if(body > ul > li:only-child) { background:green } body > div:not(body > ul > li:only-child) { background:green }
which may or may not already work in CSS3.