When I use Position Fixed on Psuedo Elements and have the background set on those Pseudo elements, jittery things happening while we scroll down the page. Please check this out. I created a sample gist . http://jsbin.com/ePibIceM/1 Mackbook Pro Retina OS X 10.8.5 Safari Version : 6.1 (8537.71)
The Same code is working Fine when I do a translateZ hack by moving the pseudo element in to layers, it is working fine http://jsbin.com/ePibIceM/3