Couple of things come to mind. 1) The image that contains everyone's head has a gap below it caused by the descendor zone of the text line (since IMG tags are inline elements and are rendered in a text line). This gap can be removed by aligning the IMG vertically to the bottom. In CSS: vertical-align: bottom; in the CSS declaration for that IMG. Setting the IMG's display CSS property to block may also do the trick. 2) Internet Explorer may just need the hasLayout DOM property tripped on the element that contains the IMG tag. The zoom: 1; CSS property and value is all it takes to trip hasLayout in IE-Win.
Most likely, you're problem stems from #1 and you just need to vertically align the image to the bottom or set its display to block.