Steve's final conclusion:

“For most web sites, the possible performance gains from optimizing CSS selectors will be small, and are not worth the costs. ”

http://www.stevesouders.com/blog/2009/03/10/performance-impa...

Exactly. I have an obsession with "optimized" markup, that means avoiding unnecessary elements, ids and classes. Let's not forget that all this stuff sits in markup and gets downloaded on each request. Even if that does not add up to much, I still want to have my code "clean". There is one particular site that inspires me: http://camendesign.com/ — take a look, not a single id or class.

He did this, however, at the expense of convoluted selectors, pseudo-elements, and pattern matching. Personally, I don't find his implementation to be very clean. I guess it's better to have the mess in your closet than wide out in the open, though.

It's not every day you can experience all the astonishment of overturning a fundamental assumption without any of the pain of forced changes. I enjoyed that conversation. (I'm Alex K, btw.)

Thanks for all the comments, everyone! Very cool to have that post picked up by Hacker News.

most of the time this certainly falls under pointless microptimisation, but if you are doing a complex web application with cpu intensive operations, it can be really handy to know how css is applied (and how reflow / redraw works) to help the user experience.