This is incorrectly marked by the validator as invalid. Border is a valid attribute when the input is of type image. It is also auto-generated by Visual Studio .Net when using an image button. If anyone has a workaround for this please let me know but I really think this should not be considered invalid code.
<input type="image" name="ctl00$ContentPlaceHolder1$IMG1"
alt="Apple IPhone" border="0" />