Hey there :)
Well, #1 float:middle doesn’t exist. You can float left or right.
You have a link so we can see what’s happening? There isn’t anything wrong with your CSS (aside from the float), so I’m assuming you more than likely have another style overriding this in IE. Try putting img.imageBorder or #containingDivClassOrSelector before the class. (where #containingDivClassOrSelecter isn’t that literally but whatever HTML tag, or class or id that this image is container within).