[superk]

Add to the failure list:

* Terrible performance - practically first rule for optimizing page rendering is "don't use CSS expressions"

http://code.google.com/speed/page-speed/docs/rendering.html http://developer.yahoo.net/blog/archives/2007/07/high_perfor...

* Only work on IE natch.

So, you have Javascript which was better performance and worked everywhere.

I think it's a little misleading to say it's the best feature no one ever used. CSS expressions were re-born as hardware-accelerated CSS3 transitions - with a much better, more focused implementation, and are pretty popular these days - especially for mobile.