CSS Performance Profiler?

Solution 1:

So, I finally got around to writing a JavaScript function that indexed all of my CSS classes on the page and then individually toggled them, while scrolling the page. This immediately pin-pointed the errant class, and from there, I was able to determine errant property. Turns out that border-radius on an element that contains many children (e.g. a body level div) performs incredibly poorly on IE9.

I've started a github repo for my CSS stress test: https://github.com/andyedinborough/stress-css

From there, you can install a bookmarklet to easily run the test on any page.

Solution 2:

The Page Speed plugin from Google has a section that analyses your CSS and tells you about inefficient selectors, perhaps start there?

hth

Note: I know its a Firefox plugin, but should help optimize a bit :)