This page examines a background-image's placement relative to the element's borders. In IE Mac borders appear to be inside the element box as the background goes behind the borders. See Safari, Mozilla, or any version of IE PC for the expected appearance.

The background image is solid black with two pixels of white on the top and left.

Depending on the width of your border, it may not be a huge issue it but could create an unsightly shift in some layouts. A simple workaround would be to offset the background-position by the width of the border initially and then hide the correct position from IE Mac like so:

div {
    border: 1px solid #000;
    background: url(2px.gif) 1px 1px no-repeat;
    /*\*/background-position: 0 0;/**/
    }