I've had a similar problem: The site had a few elements with a 1x1 pixel transparent background png and was not scrolling but jumping, continued to scroll a bit (was "laggy") and the cpu load jumped up to 100%. Changing the image size to 50x50 pixel fixed the problem.
I've had a similar problem: The site had a few elements with a 1x1 pixel transparent background png and was not scrolling but jumping, continued to scroll a bit (was "laggy") and the cpu load jumped up to 100%. Changing the image size to 50x50 pixel fixed the problem.