I've noticed that if I have a div with a width greater than 965 pixels and a border radius on less than all 4 corners, there is a stray vertical line in the div. Here's a jsFiddle link... http://jsfiddle.net/Z3vFp/4/. Notice that this only occurs in Safari. Any thoughts? Also note that the 965 pixel threshold may be a little different in jsFiddle.
EDIT: I'm on a Macbook Pro with Retina display. I guess it's an rMBP thing?
EDIT 2: Here's a jsFiddle screencap. https://i.stack.imgur.com/gHRNv.png