The four boxes should look identical: the top row's background are a png, the bottom row an svg (but they are the same image)
The background size is always 126 * the div width. On the left it is calculated as a percentage, on the right a calculated pixels value.
In chrome the right boxes are off by a pixel or so.
In Firefox the svg are drawn incorrectly.
In Safari, the right boxes are off by a considerable margin (and different in the svg and png cases).