Images used are trimed to transparcy, meaning no white space around icon.
The images are positioned using css (background-position:0 50%;)
Icons used have a even height of 70px, which results in firefox trying to position
the image in between pixels trigering the blur effect.
The images are positioned using css (background-position:10px center;)
Icons used have a odd height of 69px, which results in firefox trying to position the
image on 35th pixel (middle, 34 pixels up and 34 pixels down) not trigering the blur effect.
The images are positioned using css (background-position:10px center;)